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.Originally Posted by pos
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
~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.
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.
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/s...8&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.
POS has it right... 2235H is less sensitive in the mid-bass area.
I'd personally check in-box response before cutting into anything
Pos
Is the software you using a free version download looks neat.
Cheers
yes it is, but you can make donations.Pos
Is the software you using a free version download looks neat.
Cheers
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
Looks suspiciously like Fuzzmeasure.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 .
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 ....."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 ; Click: Cached
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
Last edited by herki the cat; 03-05-2010 at 09:33 PM. Reason: Natha
[Quote:]
Originally Posted by Loren42
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
Last edited by herki the cat; 03-07-2010 at 07:13 AM. Reason: Natha
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
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
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
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:
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.
Yes !!! How do we make our own Aquaplas ???
Verrry Interestink...ya ?
LE15-Thumper
"Give me JBL, or give me death"
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
