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Steve Gonzales
03-17-2005, 09:50 AM
I am a big fan of these awesome LF drivers and have some questions I hope can be answered. First, one of the first good buys I made in regards to vintage JBL was a pair of huge custom cabs with (2) 2231A's, (2)D216's , an LE85/HL87 and an 077 UHF per cab. One of the cabs had 2231's and the other 2205's with 2231A factory cones instead of the pleated surround stock ones. I inquired to a friend who said that this 2205A to 2231A conversion was not a problem. He then went on to say that the 136A is the same too but that for some reason, the LF response of his L300's was better than his 4333a's. I thought that the 2231A and the 136A's were identical as far as T/S parameters were concerned?. Could the LF response difference be in the crossovers?. Now, I have had some 2231A baskets with 2235H cones too. Are the T/S parameters the same for this combo, will a 2231A/2235H(cone) perform with the exact T/S parameters or is it just close? My questions are important because I am working on a project that will use one of the three depending on the answers I may get. Also, I was made aware the there are different "grades" of spiders (stiffness) and would appreciate any information as to the proper grade used in these drivers from the factory. I love the bass response with a Passive Radiator (I know, I know, it's just ME!) and would like to hear from anyone that has had or has, some Olympus SR8's or S7's. I realize that these speakers use a different LF driver but I would like to know how they perform in the LF region, hopefully, KILLER. I will thank you now for taking the time to answer these questions- THANK YOU!! -Steve G:D

4313B
03-17-2005, 10:14 AM
The 136/2231 and PR15C combo was a good one.

The 2235 cone is an evolutionary improvement over the 136/2231 cone. JBL did away with the 136/2231 cone after the 2235 cone became available. I cannot think of a single reason to seek out genuine 136/2231 cones unless someone just has to hear the difference between a 136H or 2231H and a 2235H.

Gordon W should be able to tell you all about the spider differences. Don MRitchie has also posted about the 2235H spider.

Steve Gonzales
03-17-2005, 10:21 AM
I trust your opinion that I will just go with whichever comes along at the best $. I am going to get some L300's soon and I know that they need spiders so, i hope Gordon or "The Master" might chime in on this one. Thank you Giskard

John
03-17-2005, 10:25 AM
I would bet my last donut that if you had a pair of 2231's and one of them was reconed with the 2235 kit you would be getting totally different performance from them??? I have a pair of 2231's , with one being origanel and one having the 2235 kit installed so I am curious as well what the spec's would be???
I would think the 2231http://audioheritage.csdco.com/vbulletin/images/smilies/scratchchin.gif with the 2235 kit would be the better performing one of the pair

Steve Gonzales
03-17-2005, 10:30 AM
Sorry, I didn't think to A-B them as I did have a pristine, stock pair of 2235H's at the time too, my bad. I know that the 2231a/2235H(cone) was not remarkable in the sense that it was lacking or different which reinforces what Giskard said.

Earl K
03-17-2005, 10:34 AM
Now, I have had some 2231A baskets with 2235H cones too. Are the T/S parameters the same for this combo, will a 2231A/2235H(cone) perform with the exact T/S parameters or is it just close?

- T/S will have shifted some because of an expected loss of some magnet strength for most older alnico woofers ( especially older alnicos used in the SR business ) . I would expect the first sign would be a measurable shift in Fs downwards from spec. and some loss of upper midrange response.

- I'd personally have all alnicos recharged for this reason. A partially discharged alnico will also give a higher Qts figure ( with lower Fs ). Some people will hear this combo as "more bass" / along the lines of the L100 discussion ( I won't comment ).

- If I was driving passive radiators I would want the woofer with the "most" motional control . That generally means the lowest Qts figure . So that means to be safe - I'd use ferrite magnet woofers only in this role .

- Now with all your L220s you have the necessary gear to test out those thoughts .

- Get a "beater" of an le14a. Make sure it has at least the requisite Fs. Then measure it's upper midrange response. If it's rolling off the midrange faster than the le14h ferrite counter part ( but stll has the same Fs or lower - you need to exclude the stiffer surround syndrome ) - then it's a good guess that the alnico le14a is partially demagged. Use this speaker in an AB test to a ferrite le14h.

- Compare the two ( move cabinets around so you aren't fooled by room loading ) . See if you can hear a difference in VLF control ( not quantity of ) between the two types.


- If you can't hear a difference then by all means - just use your alnico 2231/35 hybrids as is .
- If you can hear a difference then make a preference based on what you like . This may mean sticking with ferrites/&/or remagging your alnicos - or possibly - choosing a bit less motional control and a hairs more doubling/note stretching.

:cheers:

Steve Gonzales
03-17-2005, 10:37 AM
Thank you Mr. K, informative as always. :applaud:

slxrti
03-17-2005, 12:57 PM
The 2235 combined with a passive tuned to below 25 Hz can do some damage.

I compared the 136a, LE15 and 2235. The 2235 is better in every way possible.

The 2205 works will down to ~40 hz producing quality tight bass. Deeper
and as tight as a D130.

I should not have sold the 2205.

slxrti

Steve Gonzales
03-17-2005, 12:59 PM
Thank you.

Don McRitchie
03-17-2005, 01:39 PM
The biggest differences between the 2235 and 2231/136a was the introduction of a progressive suspension and high power voice coil. The progressive suspension was developed to deal with the issue of dynamic offset. At higher output levels, coil motion is no longer centered at the vertical midpoint of the coil gap but can be centered at some point outside of the gap. This greatly increases distortion. The progressive suspension acts to counteract this phenomenon and keep the coil centered. Power handling was increased with these suspension changes and the change to a kapton coil former. The result was that the later 2235 had twice the power handling of its predecessor.

Steve Gonzales
03-17-2005, 01:45 PM
Thank you Sir, I'm curious to know about these newer progressive spiders and if they are available for sale?. It sounds like I am now leaning towards the 2235H. I can kick myself for selling the pair I had but, oh well, Ed needed them at the time. Very nice to hear from you Don.


BTW: My reason for wanting just the spiders is to replace the stock one's on a less than perfect but rebuildable pair, should they need them.

GordonW
03-17-2005, 03:29 PM
These spiders are available; the correct stiffness designation (by normal reconing lexicon) for a spider for a 2231 would be a "B" stiffness, from a scale of A to E, where A is the softest, and E is the stiffest. If it's used in an 'abusive' environment, a change to a "C" stiffness spider (which is usually used in reconing a 2235) can be useful, to combat the offset issue Don mentioned. In fact, if you order an aftermarket 2235 kit, you will generally get a "C" stiffness spider.

If anyone needs these, I can readily get these spiders, at least the "C" stiffness version. I've used these in many 2235 recones, and they work just fine.

Oh, BTW: Anyone who wants a reproduction PR15C, I can build 'em. Aftermarket 2235 cone, 2231 spider (B stiffness), with a weight arrangement that is tunable like the original. I use cast aluminum baskets that are the same geometry as the JBL (usually Peavey or Yamaha PA 15" woofer baskets, they work great as those woofers were pretty much clones of a JBL 2205 or K140 anyway), and build 'em right up. Same goes for PR300s... Peavey Black Widow 12' baskets work great for making reproductions. The only thing that might hold up progress, is being able to find the baskets I want, on a moment's notice... but with the local PA reconing shop saving old baskets for me, that's usually not a big problem, as they see lots of 'em...

Regards,
Gordon.

Steve Gonzales
03-17-2005, 03:41 PM
I will definately buy from you if and when this need arrises. Thank you for the information.

duaneage
03-17-2005, 09:56 PM
I'd like to add that you could compare alnico and ferrite driver impedance peaks at Fs to determine magnet strength relative to the cone mass. Stronger magnets will yield a higher impedance value all else being equal.


PR systems have three impedance peaks so driver self control is important, amplifier dampening factor should be considered too as a source resistance added into the final Qts calculations.
My limited experience with PR systems has proven this right. I have not worked with the drivers your using but they should respond the same.

Flodstroem
03-18-2005, 06:24 AM
Hello Steve

[/QUOTE]I love the bass response with a Passive Radiator (I know, I know, it's just ME!) and would like to hear from anyone that has had or has, some Olympus SR8's or S7's. I realize that these speakers use a different LF driver but I would like to know how they perform in the LF region, hopefully, KILLER.[QUOTE]

Yeah man, I have had a pair of these S8R systems (with the LE15B version, not the usual LE15A) in a type Olympus cabinets. -Amazing deep and clean bass response.
A friend of mine statet that the sound from these speakers was "better than of the real world" :wasnt-me:

The most foolished thing I have ever made was to sell this speakers. Maybe I will never get the bass back again? :blink:

BTW, JBL had a sort of tuning chart. This chart was handy when tuning the PRīs to right weight. (I have copies)

Regards

slxrti
03-18-2005, 10:59 PM
The biggest differences between the 2235 and 2231/136a was the introduction of a progressive suspension and high power voice coil. The progressive suspension was developed to deal with the issue of dynamic offset. At higher output levels, coil motion is no longer centered at the vertical midpoint of the coil gap but can be centered at some point outside of the gap. This greatly increases distortion. The progressive suspension acts to counteract this phenomenon and keep the coil centered. Power handling was increased with these suspension changes and the change to a kapton coil former. The result was that the later 2235 had twice the power handling of its predecessor.



The changes seem minor, so if either speaker was played at a reasonable
sound level I would expect similar characteristic.


On the paper they may have similar response, but in my case there was no comparison.

slxrti

slxrti
03-18-2005, 11:17 PM
Hello Steve

I love the bass response with a Passive Radiator (I know, I know, it's just ME!) and would like to hear from anyone that has had or has, some Olympus SR8's or S7's. I realize that these speakers use a different LF driver but I would like to know how they perform in the LF region, hopefully, KILLER.


Yeah man, I have had a pair of these S8R systems (with the LE15B version, not the usual LE15A) in a type Olympus cabinets. -Amazing deep and clean bass response.
A friend of mine statet that the sound from these speakers was "better than of the real world" :wasnt-me:

The most foolished thing I have ever made was to sell this speakers. Maybe I will never get the bass back again? :blink:

BTW, JBL had a sort of tuning chart. This chart was handy when tuning the PRīs to right weight. (I have copies)

Regards


You’re not the only one, passive system when design properly can sound
wonderful. I was told to use a passive with twice the maximum excursion
of the woofer, For the 2235, that's about two inches

The funny thing, on paper the steep cut off of a passive system should have a few negative effects. But for my ears in a reverberated environment it was deep and clean.


:)

Slxrti