My Mass Rings Arrived!

[Loren42]

After I did a Fs sweep of my 2235Hs and found the Fs was the same as the 2234H, I decided to order 4 dust caps and 4 mass rings.

After some leg work I found that JBL still sells these and bought four of them. They arrived today.

I think they are made of zinc. I massed one and it weighs 33.39 grams.

http://www.mdbq.net/pyramid/massrings.jpg

Now I need to cut off the old dust caps, install these, and put the new dust caps on and the drivers should operate like they were originally designed to.

Central Florida Speaker Repar in Orlando got these for me for about $3.00 each.

Anyone ever cut off an old dust cap? I would think that I could cut them off with an Exacto-knife, but I am concerned about the affect of the magnet pulling on the blade while I work.

I can just imagine the knife blade getting sucked into the voice coil as I cross the JBL event horizon.

[JBL 4645]

Loren42
Wow what is a Mass Ring? What size are they I can’t tell by the picture?

[SMKSoundPro]

Use a sharp utility knife and slice around the dustcap a little towards the center o the dome, away from the glue line.

Be careful not to get paper bits down into the VC - gap area, so you may hold the basket on edge to keep the little particulate matter from falling in. I think you understand that gravity is not yoru friend, here.

Then, once you have sliced out the dome, keep slicing with the knife to the glueline and clean that area up of glue.

To install Mass ring. Lay a bead of glue onto the outside of the ring and place it atop the voice coil former. There is a little ridge on the mass ring so that it does not slide down into the vc former. (Don't file that off.)

Be careful not to use too much glue or it will run down into the vc gap and dry, and that is a whole nother kettle of fish!

Let the glue dry. When dried, inspect the mass ring for good adhesion, and if satisfactory, glue on new dome, again being careful not to use too much glue as, once again, its another kettle of fish.

Voila! A 2235 in born.

Any questions, just ask.
Scotty.

[jcrobso]

Loren42
Wow what is a Mass Ring? What size are they I can’t tell by the picture?
That would be the VC size of a 2335H.
As far as magnetic attraction, get one of those ceramic knifes, thay are non magnetic.;)

[SMKSoundPro]

Just use a sharp knife and be careful.

[Loren42]

Loren42
Wow what is a Mass Ring? What size are they I can’t tell by the picture?

Outside diameter is 3.893" and it is .250" tall.

On the 2235 series they installs this mass ring on the inside top edge of the voice coil former to bring the mass of the cone up from 105 grams (2234) to 155 grams. This lowers the Fs by about 3 Hz and suppresses the upper midrange SPL a few dB while extending bass response.

I bought these two JBL 2235Hs from a Craig's List sale. They were shipped across the US in a box facing each other and held together with small tie wraps. Then they were packed with white packing peanuts inside the box (just for extra protection) When I received them the tie wraps gave their lives so that the two drivers could co-mingle and flatten each other's domes.

Luckily, the damage was mostly constrained to the domes. However, when I did a Fs test I found that the Fs was actually 23 Hz instead of 20 Hz. The drivers appear to have been reconed a few years ago and my bet was that the owner cheaped out and had generic cones put in. Generic cones do not include a mass ring.

So I bought 4 rings and domes since they are so cheap and figured I would DIY the domes and if my theory was right and there are no mass rings, put them in.

Some day when genuine JBL recone kist start to get scarce I'll have them reconed, but I don't have the $500 to do that right now and this should be a good temporary fix I can live with until the day I can afford it.
You probably didn't care to hear all of that, but I am long winded by nature. :D

P.S. My avatar is a picture of one of the drivers after I opened the box - that was the first thing I saw when I opened the lid.

[Loren42]

Use a sharp utility knife and slice around the dustcap a little towards the center o the dome, away from the glue line.

Be careful not to get paper bits down into the VC - gap area, so you may hold the basket on edge to keep the little particulate matter from falling in. I think you understand that gravity is not yoru friend, here.

Then, once you have sliced out the dome, keep slicing with the knife to the glueline and clean that area up of glue.

To install Mass ring. Lay a bead of glue onto the outside of the ring and place it atop the voice coil former. There is a little ridge on the mass ring so that it does not slide down into the vc former. (Don't file that off.)

Be careful not to use too much glue or it will run down into the vc gap and dry, and that is a whole nother kettle of fish!

Let the glue dry. When dried, inspect the mass ring for good adhesion, and if satisfactory, glue on new dome, again being careful not to use too much glue as, once again, its another kettle of fish.

Voila! A 2235 in born.

Any questions, just ask.
Scotty.

Thank you!!!

I am going to try one of those Exacto knives with the smallest blade I can get. The handles are aluminum, so only the blade is magnetic.

What would you recommend for a glue for the rings?

I think Elmer's White glue is the right stuff for the domes.

[subwoof]

Ask edgewound - I believe the black "bostik" is the correct glue. you do NOT want a brittle glue here....

sub

[JBL 4645]

Loren42
I think I follow now. Good luck with the DIY provide some pictures as you go along with it.:)

[Loren42]

Ask edgewound - I believe the black "bostik" is the correct glue. you do NOT want a brittle glue here....

sub

I take it epoxy is a little too much?

[SMKSoundPro]

No epoxy!

[pos]

I don't see the point in adding a mass ring when using a digital crossover.
The 2235 is just 3dB less efficient is the midrange, the LF response remains the same. For me a mass ring is just a loss of energy (aquaplass is another story, because it can help damping the cone).

[herki the cat]

[quote=Loren42;281348]After I did a Fs sweep of my 2235Hs and found the Fs was the same as the 2234H, I decided to order 4 dust caps and 4 mass rings.Now I need to cut off the old dust caps, install these, and put the new dust caps on and the drivers should operate like they were originally Anyone ever cut off an old dust cap? I would think that I could cut them off with an Exacto-knife, but I am concerned about the affect of the magnet pulling on the blade while I work. [quote/]

Loren42 I think you are a pretty nice fellow & I hate to see you compromise those drivers with mass rings and cutting the dust cap off. I agree with Member POS on this subject. It sounds like your diaphragms already have enough mass. Any more mass will hurt the transient response & the upper frequency spectrum . Using MEK solvent to remove the dust cap can melt the foam plug in the motor pole piece vent hole, which will then drift into the voice coil gap.

Hold up for a little while. later today I can send you the CP Moyen cement & solvents data sheet if you like.

cheers herki the cat

[timc]

Will not the mass ring also help with reduce resonances?

[hjames]

I don't see the point in adding a mass ring when using a digital crossover.
The 2235 is just 3dB less efficient is the midrange, the LF response remains the same. For me a mass ring is just a loss of energy (aquaplass is another story, because it can help damping the cone).

Thanks for the charts!

I have 2234s in my L200 3ways (see avatar image), but they originally came in my 4341 4ways. I got a pair of 2235s - tried them for a while in my L200s, but when I swapped the 2 pair so the 2235s were in the 4341s, and the 2234s were in the L200s, both sets sounded MUCH better.

But it was a subtle difference.

[Loren42]

I don't see the point in adding a mass ring when using a digital crossover.
The 2235 is just 3dB less efficient is the midrange, the LF response remains the same. For me a mass ring is just a loss of energy (aquaplass is another story, because it can help damping the cone).

Thanks!

It is the midrange on my cabinets that I have too much of. Suppressing that slightly would flatten out the response and make the lower end sound more robust. Or am I missing something?

Is there any way of determining if the cones that were installed on my drivers are genuine JBL or some 3rd-party generic replacement?

I don't remember the date or the markings that were written on the cones, but it does appear that these were replaced.

It would be good to know what the pedigree of these cones are. Since I have to replace the damaged domes, I will be able to easily confirm if the mass rings are installed.

However, the measured Fs of the driver in free air was 23 Hz and I have a lot of music time on these drivers, so they should be as loose as they are going to get. The free air Fs of 23 Hz leads me to believe there are no mass rings installed.

Oh, I am using a passive crossover and a 60 WPC tube amp to drive these, by the way.

[Loren42]

No epoxy!

Thanks for the picture. I'll look for that.

[Loren42]

[quote=Loren42;281348]After I did a Fs sweep of my 2235Hs and found the Fs was the same as the 2234H, I decided to order 4 dust caps and 4 mass rings.Now I need to cut off the old dust caps, install these, and put the new dust caps on and the drivers should operate like they were originally Anyone ever cut off an old dust cap? I would think that I could cut them off with an Exacto-knife, but I am concerned about the affect of the magnet pulling on the blade while I work. [quote/]

Loren42 I think you are a pretty nice fellow & I hate to see you compromise those drivers with mass rings and cutting the dust cap off. I agree with Member POS on this subject. It sounds like your diaphragms already have enough mass. Any more mass will hurt the transient response & the upper frequency spectrum . Using MEK solvent to remove the dust cap can melt the foam plug in the motor pole piece vent hole, which will then drift into the voice coil gap.

Hold up for a little while. later today I can send you the CP Moyen cement & solvents data sheet if you like.

cheers herki the cat

Thanks, Herki.

[pos]

Thanks!

It is the midrange on my cabinets that I have too much of. Suppressing that slightly would flatten out the response and make the lower end sound more robust. Or am I missing something?

Is there any way of determining if the cones that were installed on my drivers are genuine JBL or some 3rd-party generic replacement?

I don't remember the date or the markings that were written on the cones, but it does appear that these were replaced.

It would be good to know what the pedigree of these cones are. Since I have to replace the damaged domes, I will be able to easily confirm if the mass rings are installed.

However, the measured Fs of the driver in free air was 23 Hz and I have a lot of music time on these drivers, so they should be as loose as they are going to get. The free air Fs of 23 Hz leads me to believe there are no mass rings installed.

Oh, I am using a passive crossover and a 60 WPC tube amp to drive these, by the way.
could you post pictures of the cone? (including back of the cone)
aftemraket kits usually come with no mass ring.

If you have 2234 kits attenuation of the midrange can be done in your filter. Do you have a digital active crossover?
If you are crossing low enought (no more than 300 or 400Hz) you can even handle the bump in the midrange as if it was a rising response of the driver by including it in your LP fitler slope. This is typically done by using two slopes with different crossovers points: one starts earlyer to attenuate the rising response, and the second one is right on the intendend crossover point. The eletrical slope of the filter starts to attenuate it before the crossover point, but taking the natural rising response of the driver into account, the final acoustical slope is what it was meant to be.
I think this is done on many contemporary JBL filters now, like in the 4344mk2.

I will try to do some simulation with winISD pro and post the result later

[pos]

Will not the mass ring also help with reduce resonances?
I don't think so. That would be the aquaplass.
The aquaplass reduce the HF response more than a mass ring because it reduce resonance caused by cone breakups. So if a driver relies on breakups modes to enhance its HF response (like the musical intrument drivers do) it will be much more attenuated by aquaplass than by a mass ring of the same mass.
The mass ring does not affect the cone behavior. I think that is the reason why Greg Timbers used both mass ring and aquaplass in the 251J to achieve a given balance between cone breakups, HF response, and LF extension.

[pos]

first picture just to illustrate what we already know, using the ability to add mass to a driver in WinISD Pro:
here is a 2235H and a 2234H with Loren42's 33.39 mass ring, in the same box and tuning. Same cruves, as it supposed to be.

[pos]

now the same 2234H vs 2235H curve as in post #12, but in WinISD Pro (which takes Le into account, resulting in a HF rolloff)

2235H in green, 2234H in white

(note: the ~0.3dB difference around 40Hz is likely to be a simulation artifact)

[pos]

now the same curves with a 24dB/oct L-R LP filter at 300Hz

[pos]

...and now with the addition of a small parametric eq on the 2234H:

fc=250Hz
Q=0.5
gain=-2.5dB

The two curves are now quite similar (the group delay cruves are also very similar, especially around the 300Hz crossover point)

If targeting a higher crossover point than 300Hz, a shelf filter should probably be used instead of a parametric eq (cannot simulate these with Win ISD Pro tho...)

[pos]

and the same result can also be obtained by using two slopes as mentioned above:

2235:
L-R 24db/oct @ 300Hz

2234:
Butterworth 6dB/oct @ 200Hz
Butterworth 18dB/oct @ 300Hz

So depending on the filter used, both parametric EQ and slopes management can be used to obtain the same result.

[pos]

And now the real interest of using a "managed" 2234H instead of a 2235H :

For the above response curve, here are the VA loads to achieve the same SPL (100W input power in the 2235H).

less power means less heat to dispate in the VC, which in turn means less power compression, which results in more dynamic!
(and the same goes on the amplifier side)

:bouncy:

Note: these are just simulations and WinISD Pro might not be totally accurate, so your mileage may vary on the EQ and slopes parameters, but the general trend remains the same.

some complementary info by 4313B:
http://audioheritage.org/vbulletin/showpost.php?p=2750&postcount=6

[Loren42]

could you post pictures of the cone? (including back of the cone)
aftemraket kits usually come with no mass ring.

If you have 2234 kits attenuation of the midrange can be done in your filter. Do you have a digital active crossover?
If you are crossing low enought (no more than 300 or 400Hz) you can even handle the bump in the midrange as if it was a rising response of the driver by including it in your LP fitler slope. This is typically done by using two slopes with different crossovers points: one starts earlyer to attenuate the rising response, and the second one is right on the intendend crossover point. The eletrical slope of the filter starts to attenuate it before the crossover point, but taking the natural rising response of the driver into account, the final acoustical slope is what it was meant to be.
I think this is done on many contemporary JBL filters now, like in the 4344mk2.

I will try to do some simulation with winISD pro and post the result later

Thanks. I will pull a driver and take some pictures.

The crossover is passive. See my LEAP (http://www.mdbq.net/pyramid/leap.pdf) design.

Cabinet has about 6.7 cubic feet ( a little large, but I am still adding bracing) and tuned with two 4" flared ports to 28 Hz.

Mid is the Audax PR170M0, which requires a bit more of L-pad compensation (not shown in the LEAP schematic).

[4313B]

The last time I talked with Greg about the 2235H/mass ring thing we ended up aquaplasing a pair of 2234H/2235H cones instead of using the mass rings. It worked out very well. Greg is a fan of just using the 2234H and then filling in the bottom end with EQ.

[Loren42]

The last time I talked with Greg about the 2235H/mass ring thing we ended up aquaplasing a pair of 2234H/2235H cones instead of using the mass rings. It worked out very well. Greg is a fan of just using the 2234H and then filling in the bottom end with EQ.

Talk to me about aquaplasing.

[pos]

Loren42, the easiest and best thing to do for your project would be to match the levels of the 2235 and the audax at the 400Hz crossover point, and then use some EQ to adapt the bass response to your needs (ie taste, driver caracteristics, speaker placement, and room).
The room and placement will play a huge part at these frequencies anyway, so some global EQ would be your best bet. Don't be afraid to use it!

[Loren42]

Loren42, the easiest and best thing to do for your project would be to match the levels of the 2235 and the audax at the 400Hz crossover point, and then use some EQ to adapt the bass response to your needs (ie taste, driver caracteristics, speaker placement, and room).
The room and placement will play a huge part at these frequencies anyway, so some global EQ would be your best bet. Don't be afraid to use it!

I am expecting to do that in the end, but I wanted to get my speakers in order first then when we refurbish the living room address the room acoustics as best we can. After that we can tweak the system with EQ. At least that is the plan.

On the speaker to-do list is:

Get the 2235H drivers sorted out

Tweak the passive crossovers

Squash cabinet resonances

Prep and veneer cabinets with koa.

Then... Beer-thirty :cheers:

[grumpy]

~3yrs ago, I did a near-field FR comparison between a 2235H and 2234H
in a 4430 cabinet. Attached is the difference plot (the 2235H generally being
less sensitive), 30Hz to 1KHz. [Aquaplas would be nice, but I have neither the
material, equipment, nor skill required]

Note that the compression driver was left disconnected for this measurement.

Note also that this is a hobbyist measurement, not from an accredited
lab, so... it is what it is (as you approach the limits of the plot, expect less
repeatability between driver samples, test environments, tester experience,
etc...):

[Loren42]

~3yrs ago, I did a near-field FR comparison between a 2235H and 2234H
in a 4430 cabinet. Attached is the difference plot (the 2235H generally being
less sensitive), 30Hz to 1KHz. [Aquaplas would be nice, but I have neither the
material, equipment, nor skill required]

Note that the compression driver was left disconnected for this measurement.

Note also that this is a hobbyist measurement, not from an accredited
lab, so... it is what it is (as you approach the limits of the plot, expect less
repeatability between driver samples, test environments, tester experience,
etc...):

Looks suspiciously like Fuzzmeasure. :D

Well, one thing I see is that there is about a 3 dB difference right where I really need it, the lower bass.

Maybe I am reading this wrong, 3 dB is nothing to sneeze at. It is twice the power difference.

I run a 60 WPC tube amp, so efficiency is more sought after than it might be with 300 Watts on tap.

It would seem that if I need to equalize the difference between a 2234 and 2235, I pay a bigger price with my 60 WPC amp.

Maybe it isn't that bad, but I thought I would at least bring that up.

[pos]

It would seem that if I need to equalize the difference between a 2234 and 2235, I pay a bigger price with my 60 WPC amp.
Nope, that is the other way around: the 2234H is 3dB more efficient in the midband.
So even if you have to boost the LF, it will result in exactly the same power requirement as an 2235H for the bass, and up to half the power requirement in the midband (in the 50-500Hz decade)
http://audioheritage.org/vbulletin/showpost.php?p=281478&postcount=26

boosting the LF response of a 2234H (or cutting its midrange response, which will exactly be the same with regard to power requirement) will require less power than using a plain 2235H.
That mass ring will only burn some of your power to mechanically attenuate the midrange.

[grumpy]

POS has it right... 2235H is less sensitive in the mid-bass area.

I'd personally check in-box response before cutting into anything :)

[JBL 4645]

Pos
Is the software you using a free version download looks neat.

Cheers :)

[pos]

Pos
Is the software you using a free version download looks neat.

Cheers :)
yes it is, but you can make donations.

WinISD is the simplest version, and also has a large number of JBL drivers registred:
http://www.linearteam.dk/default.aspx?pageid=winisd

WinISD Pro is also free, is more advanced (cone excursion, filter simulation, etc.), but only has a very limited number of JBL drivers pre registred:
http://www.linearteam.dk/default.aspx?pageid=winisdpro

[JBL 4645]

yes it is, but you can make donations.

WinISD is the simplest version, and also has a large number of JBL drivers registred:
http://www.linearteam.dk/default.aspx?pageid=winisd

WinISD Pro is also free, is more advanced (cone excursion, filter simulation, etc.), but only has a very limited number of JBL drivers pre registred:
http://www.linearteam.dk/default.aspx?pageid=winisdpro

I see so is it, paypal I guess the JBL 2240 and 2226 are on the site except for the JBL control 5 lol Okay i'll give it try.

Cheers :)

[herki the cat]

Looks suspiciously like Fuzzmeasure. :D

Well, one thing I see is that there is about a 3 dB difference right where I really need it, the lower bass. I run a 60 WPC tube amp, so efficiency is more sought after than it might be with 300 Watts on tap.It would seem that if I need to equalize the difference between a 2234 and 2235, I pay a bigger price with my 60 WPC amp.

Loren42, Dealing with the 20 Hz spectrum requires massive power unless you employ horns as big as house. JBL monitors have exquisite transient response and very low distortion by use use of several drivers, each of which is tailored to an opitmum spectrum band width. These systems require massive power amplifier drive, and tri-amplification with 100 t0 300 watt amplifiers is not uncomon.

Adding mass rings hurts two ways__ you loose resolution & sensitivity in the critical mid bass from100 Hz to 600 Hz, which represents the "heart of the bass spectrum" consisting of "the bass harmonic structure." Adding mass to the cone will add phase distortion & ruin whatever meager phase linearity is left in the bass, increasing progressively in descending frequency bellow 100 Hz. For deep bass,You really need to consider the massive sub woofers used in the professional JBL Movie Theater Arrays of the 3000, the 4000, and the 5000 Speaker systems, or the obsolete JBL 4686 family of subs. There is a link to a thread on JBL 4688 triple chamber sub woofer construction
via google @ http://www.google.com/custom?q=4688-...www.jblpro.com (http://www.google.com/custom?q=4688-4&sa=Google+Search&cof=LW%3A100%3BL%3Ahttp%3A%2F%2Fwww.jblpro.com%2Fj bl-pro-logo.gif%3BLH%3A100%3BAH%3Acenter%3BGL%3A0%3BS%3Ah ttp%3A%2F%2Fwww.jblpro.com%3BAWFID%3A6d393ea1cf387 9dc%3B&domains=www.jblpro.com%3Bwww.jblproservice.com&sitesearch=www.jblpro.com) .

If you want to get embroiled in the extensive "bass reproduction" theory discussions by the experts, go to the following Wikipedia Link:
Group delay and phase delay - Wikipedia, the free encyclopedia (http://rds.yahoo.com/_ylt=A0geu_Q7XZFLaxEAvQZXNyoA;_ylu=X3oDMTEzanRtcmJ mBHNlYwNzcgRwb3MDMQRjb2xvA2FjMgR2dGlkA0g1MjJfMTUy/SIG=12c7gk17i/EXP=1267904187/**http%3a//en.wikipedia.org/wiki/Group_delay_and_phase_delay) ....."Group Delay is a measure of the transit time versus frequency of a signal through a device under test (DUT) __including loud speakers especially in the bass spectrum_delay_and_phase_delay - Cached (http://rds.yahoo.com/_ylt=A0geu_Q7XZFLaxEAvAZXNyoA/SIG=180vfj4c3/EXP=1267904187/**http%3a//74.6.239.67/search/cache%3fei=UTF-8%26p=Wikipedia%2bgroup%2bdelay%26fr=hp-pvdt%26u=en.wikipedia.org/wiki/Group_delay%26w=wikipedia%2bwiki%2bgroup%2bdelay%2 bdelays%26d=YVcyoKm4UZKV%26icp=1%26.intl=us%26sig= e0eydl6eINQIi0sITLg.GA--) ; Click: Cached (http://rds.yahoo.com/_ylt=A0geu_Q7XZFLaxEAvAZXNyoA/SIG=180vfj4c3/EXP=1267904187/**http%3a//74.6.239.67/search/cache%3fei=UTF-8%26p=Wikipedia%2bgroup%2bdelay%26fr=hp-pvdt%26u=en.wikipedia.org/wiki/Group_delay%26w=wikipedia%2bwiki%2bgroup%2bdelay%2 bdelays%26d=YVcyoKm4UZKV%26icp=1%26.intl=us%26sig= e0eydl6eINQIi0sITLg.GA--)

Selected Posts on Audio Topics by John L. Murphy
Group delay and phase delay From Wikipedia, the free encyclopedia___ Group delay is a measure of the transit time versus frequency of a signal through a device under test (DUT)__ including loud speakers especially in the bass spectrum__. Group delay is a useful measure of phase distortion, and is calculated by differentiating the insertion phase response of the DUT versus frequency. Another way to say this is that group delay is a measure of the slope of the transmission phase response. The linear portion of the phase response is converted to a constant value (representing the average signal-transit time) and deviations from linear phase are transformed into deviations from constant group delay. The variations in group delay cause signal distortion, iust as deviations from linear phase cause distortion. Group delay is just another way to look at linear phase distortion.

Subject: Discussion of Group Delay in Loudspeakers (posted around 1998 to Bass List)Peter wrote:" lets considerer the trivial case of EXTREME delay at low frequencies. For source material imagine that we use a recording of a single snare drum hit. We know what a snare drum normally sounds like. Now, imagine introducing a delay of 5 seconds on the lows. Play the drum recording through such a delay and you hear the high frequency "snap" of the drum followed 5 seconds later by the lower frequency "thump" components. So instead of hearing one integrated "pop" sound we hear a "snap" followed much later,(5 s). We could all easily hear the delay in this intersting experiment.

But real speakers don't add seconds of delay. They only add milliseconds or tens of milliseconds of delay., which are indeed audible So the real question comes down to "how much delay is just audible". If we were to gradually reduce the delay in the above experiment to zero there would come a point where the delay was no longer audible as a separate distinct sound. This would probably happen above the Hass limit of 30ms or so. As the delay is reduced further there would come a point where the "delay distorted" or "time smeared" version was indistinguishable from the original recording. This delay would represent the threshold of audibility for this delay source material.

Our mission as speaker designers is to keep our group delays elow the threshold of audibility. In order to do this we need to first know what Group delay our speakers are imparting on the music, and second, know what degrees of delay are audible.


This discussion text continues with many many pages of the link.

cheers herki the cat

[herki the cat]

[Quote:]
Originally Posted by Loren42 http://www.audioheritage.org/vbulletin/images/buttons/viewpost.gif (http://www.audioheritage.org/vbulletin/showthread.php?p=281348#post281348)
After I did an Fs sweep of my 2235's and found the Fs was the same as the 2234,....[quote/]

Loren42, my apologies for complicating things. After seeing Member POS's simulated 2234/2235 curves in your bass reflex enclosure of approx 3 cu ft, it seems that a LARGER, totally sealed enclosure has not been addressed. A larger enclosure will keep the 2234 bass system FS at 23 Hz providing full response down to 23 Hz with improved phase linearity down to 23 Hz, contingent on available box damping, which is superior to a bass reflex configuration with a steep, lumpy, roll off bellow cut off, compared to the typical 6db /octave roll off of a sealed enclosure.

I have considerable experience using twin RCA, LC-1, 15 inch drivers of 20 Hz FS in each channel using a pair of 20 cubic foot sealed enclosures for left and right channels, which are large enough to keep the system FS at 20 Hz with flat response from 20 Hz up to 1500 Hz, with sensitivity reasonably adequate for your 60 watt tube amplifiers. You can have Member POS do a simulation enclosure design to accommodate one or two 2234 drivers per enclosure to keep the system resonance at 23 Hz, useful well beyond 300 Hz.

If you can procure a pair of 2440 or 2441 compression drivers from a reliable dealer (avoid the crap shoot in Ebay) & also a good set of 150 Hz cut-off, high frequency horns to cross over at 300 Hz, this will provide you with a world class system with no need to monkey with 300 watt amplifiers.

The large enclosures of approx 20 cubic feet volume can be constructed with 3/4" ply wood & a few braces & appropriate fiber glass damping internally.

Cheers Herki the cat

[Chas]

:)POS thanks for your contribution. Interesting stuff.:)

[Loren42]

Well, worth a look.

I could try doing some modeling in BassBox Pro and see what happens. No doubt that a sealed enclosure has many merits when it comes to phase/group delay.

I'll let you know.



[Quote:]
Originally Posted by Loren42 http://www.audioheritage.org/vbulletin/images/buttons/viewpost.gif (http://www.audioheritage.org/vbulletin/showthread.php?p=281348#post281348)
After I did an Fs sweep of my 2235's and found the Fs was the same as the 2234,....[quote/]

Loren42, my apologies for complicating things. After seeing Member POS's simulated 2234/2235 curves in your bass reflex enclosure of approx 3 cu ft, it seems that a LARGER, totally sealed enclosure has not been addressed. A larger enclosure will keep the 2234 bass system FS at 23 Hz providing full response down to 23 Hz with improved phase linearity down to 23 Hz, contingent on available box damping, which is superior to a bass reflex configuration with a steep, lumpy, roll off bellow cut off, compared to the typical 6db /octave roll off of a sealed enclosure.

I have considerable experience using twin RCA, LC-1, 15 inch drivers of 20 Hz FS in each channel using a pair of 20 cubic foot sealed enclosures for left and right channels, which are large enough to keep the system FS at 20 Hz with flat response from 20 Hz up to 1500 Hz, with sensitivity reasonably adequate for your 60 watt tube amplifiers. You can have Member POS do a simulation enclosure design to accommodate one or two 2234 drivers per enclosure to keep the system resonance at 23 Hz, useful well beyond 300 Hz.

If you can procure a pair of 2440 or 2441 compression drivers from a reliable dealer (avoid the crap shoot in Ebay) & also a good set of 150 Hz cut-off, high frequency horns to cross over at 300 Hz, this will provide you with a world class system with no need to monkey with 300 watt amplifiers.

The large enclosures of approx 20 cubic feet volume can be constructed with 3/4" ply wood & a few braces & appropriate fiber glass damping internally.

Cheers Herki the cat

[Mr. Widget]

Well, worth a look.

I could try doing some modeling in BassBox Pro and see what happens.It appears that a 20 cu ft sealed box will yield a system -3dB point of 98Hz and have limited power capability at lower frequencies.


Widget

[Loren42]

Mr. Widget, you beat me to it. Here are my plots with a number of permutations using the 2234 and 2235 in sealed and vented cabinets:

http://www.mdbq.net/audio/2234-2235a.jpg

http://www.mdbq.net/audio/2234-2235b.jpg

The 2234 and 2235 are not good candidates for sealed enclosures in my observation. The alignment with a Qtc of .707 is actually about 1 cubic foot. If you raise the volume the Qtc goes down very low.

MY thoughts would be that there are better drivers for a sealed enclosure than these and the Qes and Vas clearly indicate that the drivers are designed for vented enclosures.

Maybe a transmission line might be another variant worth looking at as long as you concede to a box as large as 20 cubic feet. I did some rudimentary modeling using George Augspurger's software, but there are a lot of gremlins to tame in a TL and the overall SPL level is lower than a vented enclosure, which is a drawback for a tube amp.

[LE15-Thumper]

Talk to me about aquaplasing.


Yes !!! How do we make our own Aquaplas ???

Verrry Interestink...ya ? :hmm:

[herki the cat]

Yes !!! How do we make our own Aquaplas ???

Verrry Interestink...ya ? :hmm:

Make your own Aqualuas ???, I am pleased you asked, LE15-Thumper. Early 1970's I tried to buy some Aquaplas to no avail & the Aquaplas vendor or manufacturer had a 50 gallon barrel minimum. Michael Pearce in Cal, wanted $56.00 for a small pail of the stuff. I was able to buy a 5 gallon bucket at some $30.00 from the local "Sound Coat inc.," Acoustics Products vendor; none of which i have yet to use.

But i can tell you this. "The Aquaplas appears to be a mixture of "tung oil," & maybe a little varnish and some kind of a clay body. I think the worse that can happen to the tung oil is that it may oxidize in curring, which i think is required anyway to stabilize. I have used tung oil on my wood floors since 1950 and it is extremely flexible, durable and tough.

You may find it interesting to experiment with the ingredients mentioned. One question I have pondered Aka: I have seen, & so have other people, any number of Altec 500 series horns with a 1/2 inch coat of what i have been told is Aquaplas, which has cured hard as stone. In all fairness to jBL, I have seen no proof this coating on these horns is indeed Aquaplas, & if it is Aquaplas, it may well be that a very thin, cured coat is mechanically resistive to bending & does function perfectly well and stabile as excellent damping on a speaker cone or diaphragm.

Chears herki the cat

[Loren42]

I have seen, & so have other people, any number of Altec 500 series horns with a 1/2 inch coat of what i have been told is Aquaplas, which has cured hard as stone.

My understanding is that it is also available as a paste, so it may very well be what you describe.

[herki the cat]

A little review & a parting thought:

[quote=Loren42;281912]Mr. Widget you beat me to it.

[quote Mr. widget]
The 2234 and 2235 are not good candidates for sealed enclosures in my observation. The alignment with a Qtc of .707 is actually about 1 cubic foot. If you raise the volume the Qtc goes down very low.

MY thoughts would be that there are better drivers for a sealed enclosure than these and the Qes and Vas clearly indicate that the drivers are designed for vented enclosures. [quote/]

[Quote 4313B]
Greg ended up aquaplasing a pair of 2234H/2235H cones instead of using the mass rings. It worked out very well. Greg is a fan of just using the 2234H and then filling in the bottom end with Q. [quote/]



I have 2234s in my L200 3ways (see avatar image), but they originally came in my 4341 4ways. I got a pair of 2235s - tried them for a while in my L200s, but when I swapped the 2 pair so the 2235s were in the 4341s, and the 2234s were in the L200s, both sets sounded MUCH better. But it was a subtle difference.

Loren42, The 2234, and 2235 have a good reputation; Hjames obsevered only a very slight difference in the sound of the two drivers in her L300__ It seems that you can only use these drivers the way they were designed for a JBL speaker system. Monitor design is extremely complicated, employing cone speakers designs of sophysticated topology trade-offs adapted to yield excellent performance in reasonable size enclosures. There is no problem with the The matching superb JBL compression high frequency compression drivers & matching horns. Complexity of time alignment of the horns is accommodated by JBL digital delay active cross overs rather well.

It may be to your advantage to completly duplicate the widely acclaimed L200 Systems while parts are still available.

Herki

[Loren42]

A little review & a parting thought:

[quote=Loren42;281912]Mr. Widget you beat me to it.

[quote Mr. widget]
The 2234 and 2235 are not good candidates for sealed enclosures in my observation. The alignment with a Qtc of .707 is actually about 1 cubic foot. If you raise the volume the Qtc goes down very low.

MY thoughts would be that there are better drivers for a sealed enclosure than these and the Qes and Vas clearly indicate that the drivers are designed for vented enclosures. [quote/]

[Quote 4313B]
Greg ended up aquaplasing a pair of 2234H/2235H cones instead of using the mass rings. It worked out very well. Greg is a fan of just using the 2234H and then filling in the bottom end with Q. [quote/]



Loren42, The 2234, and 2235 have a good reputation; Hjames obsevered only a very slight difference in the sound of the two drivers in her L300__ It seems that you can only use these drivers the way they were designed for a JBL speaker system. Monitor design is extremely complicated, employing cone speakers designs of sophysticated topology trade-offs adapted to yield excellent performance in reasonable size enclosures. There is no problem with the The matching superb JBL compression high frequency compression drivers & matching horns have no problems. Complexity of time alignment of the horns is accommodated by JBL digital delay cross overs rather well.

It may be to your advantage to completly duplicate the widely acclaimed L200 Systems while parts are still available.

Herki

Yes, I was trying to show that a sealed design is not the way to go.

If you have been following my other threads about this speaker build you can see that it is coming together and I think that I will get a pretty good system out of it in the end. My biggest problem appears to be the room, but that is another topic.

My vented cabinet is a 3-way with almost 6.7 cubic feet. That will go down some when I add more internal bracing and cabinet wall treatments.

My F3 is currently at 33 Hz (according to BassBox Pro with the box tuned to 30 Hz) and I am left with dialing in the crossover networks and then working on improving the cabinet resonances. The JBL is currently crossed at 400Hz.

My intent was to bring my drivers up to JBL spec because that was what my cabinets were designed to.

The idea of utilizing 2234H drivers due to their improved mid bass is tantalizing. I am just not sure which way to go yet.

Here is an old link to my cabinet design:

Pyramids (http://web.me.com/mdebeque/Site/Pyramid_Speakers.html)

The web page needs updating. I have replaced the mids with Audax PR170M0 drivers ( see here (http://www.mdbq.net/pyramid/pyramid.jpg) )and this crossover (http://www.mdbq.net/pyramid/leap.pdf).

Once all that is done I have some very nice koa veneer waiting to be applied to the boxes. :)

[Ruediger]

1.) If You don't know if the cones are aftermarket or original, why don't You measure the Thiele Small parameters?

2.) Did You yet take Your amplifier's output impedance into account?

Ruediger

[herki the cat]

In my other threads, my speaker is coming together as a pretty good system. My problem appears to be the room,= another topic. Utilizing 2234H drivers with improved mid bass is tantalizing. Here is an old link to my cabinet design; I have some very nice koa veneer to apply to the boxes. :)

click: Pyramids (http://web.me.com/mdebeque/Site/Pyramid_Speakers.html) to view image of Loren42's Pyramids Speakers...

Loren42, your "Pyramids" Enclosure's are absolutely gorgeous, & do represent a tremendous professional work of art. I had no idea since i chimed in on the last page of the 2234/2235 issue.

You may wish to refine the (speaker vs room) artifacts issue, and investigate the speakers isolated from the room, perhaps out of doors. I have found that even when the speaker system has a very smooth, flat, measured frequency response, that Ringing or Hangover modes may persist after the drive signal ends due to speaker system hang-over ringing undamped artifacts, which represent "duration of sound energy" equivalent to the perceived increased loudness properties of room reverberation.

The explanation is that "perceived, increased loudness" occurs acoustically in two ways. (1)...Increasieing the signal amplitude, or (2)...Adding duration to the signal, which is equivalent to natural room or auditorium reverberation sound, because that sound continues to stimulate the hearing function of the ear after the original direct sound has ceased; This loudness characteristic of reverberation becomes more intense, inversely proportional to frequency, particularly noticeable at the lower frequencies in the mid bass spectrum due to decreasing attenuation of sound energy propogating in air. This is how a nice big auditorium enhances the sound of an orchestra, which would otherwise sound like a" mashed potato sandwich" with the orchestra performing out of doors in a cow pasture.

This test is very easy to perform by using a "tone burst" generator and oscilloscope to view the the speaker output with a microphone. A tone sweep from 20 Hz to 20,000 Hz in slow incremental steps is interrupted after eight cycles of stepped frequency for viewing any hang over in speaker output during g eight cycles of zero signal application to the driving amplifier. Any hang over ringing lasting more than 1/2 cycle is considered to be "not acceptable."

I will be comunicatingwith you via Email.

Herki

[Loren42]

In my other threads, my speaker is coming together as a pretty good system. My problem appears to be the room__ another topic. Utilizing 2234H drivers with improved mid bass is tantalizing. Here is an old link to my cabinet design; I have some very nice koa veneer to apply to the boxes. :)

click: Pyramids (http://web.me.com/mdebeque/Site/Pyramid_Speakers.html) to view image of Loren42's Pyramids Speakers...

Loren42, your "Pyramids" Enclosure's are absolutely gorgeous, & do represent a tremendous professional work of art. I had no idea since i chimed in on the last page of the 2234/2235 issue.

You may wish to refine the (speaker vs room) artifacts issue, and investigate the speakers isolated from the room, perhaps out of doors. I have found that even when the speaker system has a very smooth, flat, measured frequency response, that Ringing or Hangover modes may persist after the drive signal ends due to speaker system hang-over ringing undamped artifacts, which represent "duration of sound energy" equivalent to the perceived increased loudness properties of room reverberation.

The explanation is that "perceived loudness" occurs acoustically in two ways. (1)...Increasieing the signal amplitude, or (2)...Adding duration to the signal, which is equivalent to the natural room or auditorium reverberation sound, because that sound continues to stimulate the hearing function of the ear after the original direct sound has ceased. This is how a nice big auditorium enhances the sound of an orchestra, which would otherwise sound like eating a "mashed potato sandwich" with the orchestra performing out of doors in a cow pasture.

This test is very easy to perform by using a "tone burst" generator and oscilloscope to view the the speaker output with a microphone. A tone sweep from 20 Hz to 20,000 Hz in slow incremental steps is interrupted after eight cycles of stepped frequency for viewing any hang over in speaker output during g eight cycles of zero signal application to the driving amplifier. Any hang over ringing lasting more than 1/2 cycle is considered to be "not acceptable. "

I will be comunicatingwith you via Email.

Herki

The term 'hang over' is new to me. I probably know it by anther term, but if you could define it for me I would be grateful.

I believe I have some rather incredulous room issues. Look at this far field plot at my current listening position:

http://www.mdbq.net/pyramid/m10.jpg

I plan to run a plot with one of the speakers outside, but Florida is not cooperating right now. The temperature is nice, but we get a lot of wind and I need a calm day to do this right.

Florida has another issue and that is most homes make spacious use of ceramic tile. We have lots of tile in our house and surprisingly, it makes a very good acoustic mirror. :)

While you can do gated measurements, the floor makes this problematic. I have tried carpet pieces laid down before the speaker and have had little help.

This is one of the issues with the room, which is currently set up like this:

http://www.mdbq.net/pyramid/layout1.jpg

The living area shares space with the kitchen, so I have a pretty live room with lots of nodes and antinodes (as proven by my room sweep). We have a room renovation on the radar screen some day in the future and that will be the best time to figure out room treatments. Meanwhile I want to get the speakers dialed in.

Near field and ground plane measurements do hint at a reasonably flat response so far. I expect when the cabinets are dragged outside that those measurements will confirm a good response. I also need to take off-axis responses so that I can tweak the crossover design.

Lastly, if hang over is related to cabinet resonances, then that is another issue to work on with these cabinets. I bought an accelerometer and will be doing a baseline on the current cabinets and then work on inner wall treatments to reduce wall ringing. I may first build a test box with a removable panel that I can try different techniques, including constrained layering, to minimize wall resonances.

So, as I said before, my original design path was with the 2235H. Realizing that a 2234H may offer better mid bass is a consideration that I need to work out... Door number one... or door number two??? :)

[Loren42]

1.) If You don't know if the cones are aftermarket or original, why don't You measure the Thiele Small parameters?

2.) Did You yet take Your amplifier's output impedance into account?

Ruediger

1. I did the Fs, but I did not do the rest of the measurements (as described in Vance Dickason's book). When I saw 23 Hz as the measured Fs I sort of got suspicious and ordered rings just in case. They are cheap at $3 each, my domes are crinkled up and need replacement, so I thought, "why not?"

2. I figured the amp's impedance at 1 Ω.

[Ruediger]

1. I did the Fs, but I did not do the rest of the measurements (as described in Vance Dickason's book). When I saw 23 Hz as the measured Fs I sort of got suspicious and ordered rings just in case. They are cheap at $3 each, my domes are crinkled up and need replacement, so I thought, "why not?"

2. I figured the amp's impedance at 1 Ω.

I don't know what kind of equipment You use and what Your measurement error is. But there will be some error. Also the 20 Hz resonant frequency are an average value with some error. The 23 Hz might be the result of a slightly-out-of-spec 2235 and some measurement error.

You should measure the whole set of TS parameters so that You know what kind of animal You have.

1 Ohm amplifier output impedance is a lot. The series coil in the crossover will add some more resistance. You need to calculate the resulting total Q. For this Qt You can then design a box.

Ruediger

[Loren42]

I don't know what kind of equipment You use and what Your measurement error is. But there will be some error. Also the 20 Hz resonant frequency are an average value with some error. The 23 Hz might be the result of a slightly-out-of-spec 2235 and some measurement error.

You should measure the whole set of TS parameters so that You know what kind of animal You have.

1 Ohm amplifier output impedance is a lot. The series coil in the crossover will add some more resistance. You need to calculate the resulting total Q. For this Qt You can then design a box.

Ruediger

I can see that.

One thing I do need to do is replace the paper domes. Once I take that off I will know if it is a 2235H or 2234H by observation.

The sticking point now is not so much whether it does or does not have the mass ring, but if it doesn't have a mass ring, should I install one?

There have been some compelling arguments that a 2234H would be a better driver (assuming that I EQ the mid bass down about 3 dB). I just have not made up my mind yet. That's the conundrum. :blink:

[Ruediger]

I can see that.

One thing I do need to do is replace the paper domes. Once I take that off I will know if it is a 2235H or 2234H by observation.

The sticking point now is not so much whether it does or does not have the mass ring, but if it doesn't have a mass ring, should I install one?

There have been some compelling arguments that a 2234H would be a better driver (assuming that I EQ the mid bass down about 3 dB). I just have not made up my mind yet. That's the conundrum. :blink:

So the question is "which is better? 2234 or 2235". Simply look up the TS params for the two speakers and check which of them allows for the Thiele alignment which suits You best.

Given the high output impedance of Your amplifier You 1st need to take that into consideration, as well as the DC resistance of the series coil in Your crossover (make an educated guess**). You need to calculate the resulting Qt.

I would not at all care about group delay, slew rate, aquaplasing etc. JBL has designed the two woofers, with excellent results. Both drivers are good up to 1 kHz. What else do You want?

I do have only very bad copies of Thiele's tables. If I would scan them again nobody could read them. DOES ANYBODY HERE IN THE FORUM HAVE GOOD COPIES OF THIELE'S PAPERS?

Let's stay tuned. Ruediger

[Ruediger]

Take the crossover for the 4430, check the inductivity (mH) of the series coil. Look up the prices for different forms of coils with that inductivity (forget the coreless ones), see how much You need to pay for a small DC resistance.

Ruediger

[Ruediger]

I found copies in reasonable quality on the net and published them in the General Audio Discussion group.

Enjoy!
Ruediger

[Loren42]

So the question is "which is better? 2234 or 2235". Simply look up the TS params for the two speakers and check which of them allows for the Thiele alignment which suits You best.

Given the high output impedance of Your amplifier You 1st need to take that into consideration, as well as the DC resistance of the series coil in Your crossover (make an educated guess**). You need to calculate the resulting Qt.

I would not at all care about group delay, slew rate, aquaplasing etc. JBL has designed the two woofers, with excellent results. Both drivers are good up to 1 kHz. What else do You want?

I do have only very bad copies of Thiele's tables. If I would scan them again nobody could read them. DOES ANYBODY HERE IN THE FORUM HAVE GOOD COPIES OF THIELE'S PAPERS?

Let's stay tuned. Ruediger

Actually, what would be more valuable would be the "acoustic data" for the 2235 and 2234 so I could import it into Bass Box Pro and Xover Pro. Even better would be the acoustic data for my woofer!

I have the T/S parameters already in the BassBox Pro library, but there is no acoustic data for those drivers nor my Audax midrange.

I don't understand the procedure to generate my own acoustic data from my drivers nor what tools I would need to do it. Anyone have clues?

I believe this data is then input into the "Response" tab of the library driver data. Having this data will allow me to more accurately model my crossover and box.

[Loren42]

I pulled one of my JBL 2235Hs from the cabinet and checked the inscribing on the back of the cone.

I feel comfortable that they were, in fact, reconed as 2235Hs after all using JBL parts.

The cone back has the JBL cartouche on the cone that reads:

JBL
PRO
21

with a white circle around it. Hand scribed on the other side is 2235H. There are some unintelligible signature and the presumed serial number:

50320

I would assume that the mass rings were installed if the cone is hand marked 2235H, but I need to replace the domes and when I do I will confirm if the rings are present. If they are I do not intend to try to remove them.

I can also assume the recone used genuine JBL parts, which makes me happy, too.

[herki the cat]

I pulled one of my JBL 2235Hs from the cabinet and the inscribing on the back has 2235Hs plus serial number:50320. I need to replace the domes. I will confirm if the rings are present.

Looks like you are on the verge of working out the rest of your speaker design which will require enclosure frequency response measurements.This will necessitate covering up that entire tile floor with a wall to wall thick rug, which for good sound absorption should have a wall to wall under-pad of "Ozite"-- Brand Name," wool & cow hair construction. This is the material used by Dr Harry Olsen on all six sides of the RCA Princeton Laboratories Anechoic $1,000,000 quiet room. For the treatment on walls & ceiling, please consult member EarlK's recent excellent LH Forum threads & posts on this subject.

The JBL tube of C.P. Moyen Inc., cement shown in a recent thread uses Acetone solvent which is similar to MEK solvent. Both of these solvents have fumes which will cause the foam in the motor pole piece vent hole to revert to a gooey mess of liquid polyurethane that will find its way to the voice gap.

It is suggested you should call C. P. Moyen Inc., Customer service @ 874-673-6866 to explore an RS Cement of toluene solvent compatible with foam, paper cones & caps. BTW, Toluene IS compatble with foam surrounds.

herki

[Loren42]

Looks like you are on the verge of working out the rest of your speaker design which will require enclosure frequency response measurements.This will necessitate covering up that entire tile floor with a wall to wall thick rug, which for good sound absorption should have a wall to wall under-pad of "Ozite"-- Brand Name," wool & cow hair construction. This is the material used by Dr Harry Olsen on all six sides of the RCA Princeton Laboratories Anechoic $1,000,000 quiet room. For the treatment on walls & ceiling, please consult member EarlK's recent excellent LH Forum threads & posts on this subject.

The JBL tube of C.P. Moyen Inc., cement shown in a recent thread uses Acetone solvent which is similar to MEK solvent. Both of these solvents have fumes which will cause the foam in the motor pole piece vent hole to revert to a gooey mess of liquid polyurethane that will find its way to the voice gap.

It is suggested you should call C. P. Moyen Inc., Customer service @ 874-673-6866 to explore an RS Cement of toluene solvent compatible with foam, paper cones & caps. BTW, Toluene IS compatble with foam surrounds.

herki

Thanks for the information.

I think that I will try dragging the cabinets outside on a calm day first. Florida is pretty breezy and the next calm day is predicted Wednesday. That is a lot cheaper than a lot of carpet, but in the final room setup we should consider some sort of carpet between the cabinets and the sofa.

Speaking of the final room orientation, yesterday we temporarily moved the room to its new position and set the speakers near the corners. I had a guest over to audition the system (amp and speakers) and he brought some test CDs including Hector Berloiz Symphony Fantastique. We cranked up the system to a good listening volume, which was modestly loud. This CD has a very wide dynamic range and it appears a lot of sub sonic rumble as well. The left woofer found its inward excursion limit on track 5 with a loud sharp whack about 3 to 5 times before I dropped the volume slightly. It was either the voice coil bottoming out or the mass ring hitting the pole (probably the latter). I need to consider a rumble filter.

Nevertheless, my friend was quite excited with the performance. He said that only twice in his life had he ever felt a concrete slab floor vibrate. The first was when he auditioned a pair of B&W 801s and then this system here.

The tube amp never spit out anything offensive for the whole performance. Having extra capacitance in the high voltage power supply really pays dividends when you need serious transients, particularly bass. Seemed to just loaf along.

I'll research the glues.