"hybrid" reconed drivers: Sound & t/s para. Issues: Any available info ?

[RMC]

Many drivers out there had to be reconed (or re-foamed) with different recone kit (or re-foam kit) than the original stuff, for reasons of availability, cost, etc. I don't recall seeing something written on this matter with some science, like actual measurements done, or experience in the field described after job done, and comparison with the original's sound and/or specs, particularly T/S parameters. It would be interesting to know what fellow members have to say about this in terms of sound and/or measured specs. Some measurements are relatively simple, like Re Voice coil resistance or Fs Free air driver resonance, while others are more complicated to do. Big sound difference ? Large deviations in specs ? Please jump in and let me know your comments or experiences.

Here's a specific example (many others possible) from another thread with regards to a JBL driver:

Out of curiosity, why 2225H (recones) on E-140 frames for the 4520 ? Why not E-140 recones ? Or 2225H recones on 2225 frames ? Only thing available/on hand ? Cheapest solution (money, ya that bugger)? For the longer cone travel of 2225 (5mm) VS E-140 (3.56mm)? For the smaller .17 Qts of the E-140 (closer to 2205 Qts of .21) compared to 2225's .28 Qts ? Since there's a lot of other "hybrids" out there (e.g. 2205 reconed with 2225), I have always wondered what happens in these cases to driver specs T/S parameters, a mix of both ? And how does the driver reacts in the box: acoustically like a 2225H but electrically like a E-140 ? A mix of both ?

Richard

[Ed Zeppeli]

JBL used the same frame/basket to make multiple speakers; the qualities of which were determined by the cone characteristics. 2234, 2235, 2205, 2225 are interchangeable, for example.

Or are you talking about aftermarket kits?

http://www.audioheritage.org/vbullet...ight=mackenzie

[RMC]

Thanks Ed for your reply and the 2011 thread I didn't have. Both very interesting. I was talking about BOTH possibilities (OEM recone on different frame/basket and aftermarket recone on same basket), with potential results available in terms of sound and/or T/S parameters actual experience members had.

As for the same frame/basket used by JBL for many drivers and qualities determined by the cone's characteristics, I note as an example in your list 2205/2225 as being interchangeable, but if you remember some of the parameters of the two are quite different, in the following order 2205/2225:
Fs 30/40HZ ; Qts .21/.28; Vas 297.3/170 liters; X max is also different. These differences are substantial here. So after a recone job will that 2205 now be considered for all practical purposes a 2225 ? The impact on driver suitability for a particular box could then switch from go to no go...

The example I gave about 2225 recones on E-140 frame was a question I asked EAULIVE (I just noticed he's in the 2011 thread) in a recent thread about 4520 cabinets but he didn't provide a reply on that issue. Since I MAY have to do some work on my JBL drivers in the near future I'm interested in knowing...

Richard

[Ed Zeppeli]

As for the same frame/basket used by JBL for many drivers and qualities determined by the cone's characteristics, I note as an example in your list 2205/2225 as being interchangeable, but if you remember some of the parameters of the two are quite different, in the following order 2205/2225:
Fs 30/40HZ ; Qts .21/.28; Vas 297.3/170 liters; X max is also different. These differences are substantial here. So after a recone job will that 2205 now be considered for all practical purposes a 2225 ? The impact on driver suitability for a particular box could then switch from go to no go...

Do you not feel that these differences could be explained by the cone alone?

I'm not an expert here, but I do know that after extensive research here I reconed some 2205s (not 2205A) as 2235Hs successfully using OEM kits.

[Eaulive]

I invite you to this read:http://www.lansingheritage.org/html/...s/tech1-3a.htm
You should be able to make up your own mind about mixing cone kits and frames ;-)

[RMC]

Hi Ken and Warren,

Glad you're still hanging in there pending Flodstroem's reply with an actual computer speaker software simulation regarding a recone into a different frame/basket (e.g, 2225 recone into E-140 frame) and impact on driver specs/performance.

KEN "Hope it was actually helpful."

Yes it is, as usual, now I know for sure what my options are since my now 36 years old 2205H's spider, surround, voice coil former, etc. won't last forever... So at one point in the near future I'll probably need two better made recone kits for these, because I tend to cherish and keep my good stuff a long time. That's why I prefer purchasing quality gear lasting many years (Rane, QSC, Tascam, Mackie, etc., 20+ years !).

"I must confess...I've can't remember ever seeing a 2205H in for recone. They must be pretty rare, since there are TONS of 2225s out there."

When I purchased these brand new in 1981 they had recently been converted from Alnico to Ferrite (late 70's or early 80's) and probably near the end of the production cycle, since, if my memory is correct, the 2225H came out in 1982 or so...

"I just had a 2245H kit through eBay's Global Shipping program delivered to Switzerland today that was damaged upon delivery. It was real pretty, too! Oh well...that's what insurance is for, right?"

That's a real bugger for me sending my drivers far away (from eastern Canada to west coast USA, about 3,000 miles) to get them reconed for example. Most likely they would arrive in California barely good enough for the dumpster, and if not, then for sure on the way back here, knowing Canada Post handling...

My drivers are also real pretty for their age and, unfortunately, no insurance can replace this obsolete model... So, ordering a best fit/better made recone kit from the USA is about the only practical option I can see...

WARREN "They just happened to be available and affordable for me to use as cores..."

Not so for me, I purchased them because I really liked the sound of these drivers, mounted in vented-boxes in a biamp system with satellite speakers (home playback system).

Richard

[edgewound]

Opps....I think I forgot to address a couple of other issues.

The 2225H and/or 2226H are very much suitable replacements for the the 2205H. They will sound different because they are different in a few aspects, so it's best practice to replace them all with the same model. Since aftermarket parts are available for them all they can either be reconed with original spec parts or updated...this being the 2205 and 2225, since the frames/motors are in fact identical.

The 2226 is a whole different animal and can only accept 2226 or VGC style voice coil in the motor. These are not interchangeable with previous generation SFG and/or AlNiCo motors...which are interchangeable since the voice coils are the same ID.

[RMC]

ED I do not know for sure yet (not yet convinced) if the differences could be explained by the cone alone. That's why I'm seeking input from other members who have gone through the process, and maybe took some measurements of the results. Perhaps of more importance to me here is the fact YOU did reconed 2205 to 2235H successfully using OEM kits. I'm relying (with no doubt) on your ear to say this was a success. That's helpful.

What about some numbers others MAY have measured ? Other experiences good or bad and why ?

EAULIVE did reply today re 2225 recones on E-140 frames in the other thread I had on 4520 cabinets. I hereby transfer his interesting reply in this thread:

"Originally I was planning on loading the cabs with 2225s but since I had a bunch of E140 frames on hand I checked the possibility and tried to predict the behaviour of the E-140/2225 mix.
Both frames have the same gap width and length, the only difference lies in the magnet strength. The 2225 has a 1.2T motor while the E-140 has a 1.35T motor so I figure after much reading here and elsewhere that the only difference would be in higher frequency response outside the band I was planning to use them (my 4520s are crossed at 150Hz with my midbass horn) so I went with that.
Besides, I don't like the aluminum dust cap on a speaker system that is intended to be a sound "reproducer", not a sound "producer"

A friend had original 2225s so we swapped them for fun and did not see a difference for that specific application (4520s crossed at 150Hz)

As for the other "mixes" a 2225 on a 2205 frame is basically a 2225 because the frame and magnet structures are identical, the big NO-NO is using these cones on a 2220 frame as I saw in the past... Lee will remember the source of my 4520s and the drivers the guy wanted to push on us ;-) "

I thank both of you for the "food for thought". I'm still chewing on that. I will read again JBL's Tech note # 1-3A which I had and looked at a longggg time ago.

Don't hesitate to come back.

Richard

[Flodstroem]

Data tells me that the "woofer" is not getting to be as the original (2225):

Both frames have the same gap width and length, the only difference lies in the magnet strength. The 2225 has a 1.2T motor while the E-140 has a 1.35T motor so I figure after much reading here and elsewhere that the only difference would be in higher frequency response outside the band I was planning to use them (my 4520s are crossed at 150Hz with my midbass horn) so I went with that.

You/he has described some of the baskets as heaving the same dimensions BUT different magnetic strength. In the next setting it says the only difference would be in the higher frequency response outside the band (in use). It couldnt be that because the Bl-product is different. That means the voice coil built for a 1.2T is now going to work in a different magnetic strength. The Bl product is changed for that 2225 woofer with a factor of approx 1.125. It means the Tiele/Small parameters has change in the whole frequency band, not only in HF. For example, Fs has risen and that means a lot. You can not put a voice coil in a stronger magnetic motor and then say it is the same woofer in the LF band. Its easy to see that for example in a bass box simulation program. Thats my experience so far.

[RMC]

Speaker driver manufacturers, such as JBL, rarely sell original re-foam kits for their woofers, the norm being a complete recone kit, and in JBL's case installed by a JBL certified reconing shop (for quality of work) or nothing... Yes, its all or nothing.

Naturally, the situation has lead not only to prosper aftermarket recone kits businesses, but also to the creation of another booming sector: the re-foaming business, which includes DIY. Because most aftermarket manufacturers or vendors don't provide (except dimensions/material) customers with much valuable info (e.g. T/S values), we have to try to find relevant specs on our own (like chasing ghosts) or actual measurements done (few do it), including on the impact on performance of using aftermarket stuff. Then, the decision to go ahead would be an informed choice, as it should be, contrary to "the blind leading the blind" type of situation.

Since aftermarket foams/cloth surrounds are not the original JBL stuff, my concern with ANY different surrounds (including mine; same with any non-original recone kits) is will it fly according to flight plan ? In other words, deliver comparable/equivalent performance so that driver AND box parameters are not materially affected (I'm not concerned with such tiny things as Barry's 1 hz difference on Fs measurement, plus its well within production tolerances). Initially, I must say I have some doubts about the equivalent nature (quality, performance, specs, T/S) of the "clones". But I'm quite open to be proven wrong by science or actual measurements. Will I have to take back or nuance SOME of what I said ?

Barry's experiment with Butyl rubber surrounds on JBL 2234 drivers (he's quite delighted with these), appears to give him a headstart on me. With the type of gear and knowledge he has, Its doubtful Barry would have purchased the first surrounds that met the eye, no questions asked. Considering he likes his things proper, as I do, he must have done his homework before jumping into this unconventional rubber surrounds "adventure" for 2234 (Didn't he say if you value your time recone?). So his thing is probably more an "educated guess" than a simple "flip the coin" type of decision.

In my case, to re-foam my 12" JBL drivers I spent time searching for a surround model with similar foam material that not only looked and measured like the original (thickness ?), but was also specifically made for the 2214H, hoping to increase my chances of getting equivalent performance. Did I wasted time and money in doing so, compared to cheaper generic/standard foams ? I don't think so re 2214 foam width.

Re-foam vendors typically claim to bring the speaker back to life at a fraction of the cost of new drivers. Not much more than that, except for mine they claimed these new surrounds last much longer than the original foam (one of Barry's reasons to go with "rubbers" is their longevity VS the re-foaming hassle, agreed). We all know a re-foamed driver will still reproduce sound. Doing it very well is even nicer. How good of a reproducer the modified driver be in that specific box, is the real issue. Is it still optimal or close enough ?

Logically, surround material types (e.g. rubber VS foam) should have an influence, unless both materials used have about the same specs (which we don't really know in this context). Are both materials equally compliant for example? Their thickness the same ? (thicker more rigid, thinner more compliant). I don't recall seeing something on this subject of materials' properties/data with regards to surrounds (other than cloth VS foam).

Finally, the re-foam (or even recone) done and its relation to the selling of the driver. Barry's drivers are probably not for sale, same for me. But what would happen if such vintage drivers were on the market for a new owner? Would a prospective buyer hesitate or downgrade the value (appearance, quality of work, performance) because of the non-original or unconventional surrounds ? Could it be more difficult to convince that buyer that these are equivalent, plus better lasting surrounds ? Tough questions. Depending on what I'm looking at (condition) and asking price, maybe I would hesitate. Or be tempted to discount the price... So if not an original job done, it may have a negative impact on selling price, unless you can prove your claims (e.g. measurements, extensive listening tests, dated invoice, etc.). I think I hear Ken's voice...

TO BE CONTINUED IN THE NEAR FUTURE WITH PART 2. I haven't finished yet "assembling" in a logical way the expert's views I have found on some relevant issues. Plus I have other things to attend or the wife will... me.

Richard

P.S.: Barry mentioned to me "...will try to find some of my own hybrid driver measurments." Real life stuff, icing on the cake, makes it even better! That would be interesting to see after Part 2 to compare expert views with user results... It seems DAVIDPOU here may also have some after re-foaming measurements.

[RMC]

The search continued for some data regarding the use, among other "Hybrids", of a recone kit (e.g. 2235H) into a different frame/basket (e.g. E-140). I have found two older Threads on this site dealing with an aspect of this Hybrid issue, and giving some interesting results in terms of T/S parameters. It confirms a good part of what fellow member Flodstroem was saying in the present thread. Here are the names of the two Threads of interest started in 2004 and 2005, both in the "Lansing Product Technical Help" section. Don't be fooled by their title, they ARE quite relevant with hybrid category of a recone kit into a different basket:

Thread: Does anybody know the M32-8, 15"? Recone to 2235H question... , started May 7, 2004
Of particular interest, see posts # 7 (Mr. Widget), 13 (4313B-Giskard), 16 (Mr. Widget) and 17 (Ralf).

Thread: E140 = 2225??? , started Nov.4, 2005
Also of particular interest, see posts # 2 & 3 (Lancer), 7 (Rob), 10 (Lancer), 11 (Ian), 12 & 25 & 33 (Zilch), 36 (Ian) and 65 (Thom).

In summary, many of the older and popular JBL 22 series drivers have a Flux number of 1.2 Tesla (except 2215, 2220, etc.), contrary to the E-series 120, 130 and 140 with a Flux of 1.35 Tesla. So installing such a 22 series recone kit into an E-series basket named above WILL lead to a change in a number of T/S parameters in such a way that the hybrid driver will not behave exactly as the recone kit number would suggest due to the stronger motor...

Originally Posted by Giskard

The 1.35 T*m assembly (E140 for example) uses the 7/8" thick magnet and the 0.280" top plate.

The 1.20 T*m assembly (2235H for example) uses the 3/4" thick magnet and the 0.280" top plate.

The 1.15 T*m assembly (2220H for example) uses the 3/4" thick magnet and the 0.350" top plate.

The 0.95 T*m assembly (2215H for example) uses the 7/8" thick magnet and the 0.600" top plate.

Originally Posted by Giskard

Two different cores, stock 2225/2235 1.2 T*m core and E130/E140 1.35 T*m core.

Red signifies changes from stock 2234H and 2235H.


See Tables, Lists and Graphs in the Threads/Posts identified above for details. Good reading.

Richard

[RMC]

Hi to my Norwegian friends ! I worked for Norway's Kvaerner for many years in Canada...

Apart from that, I'm really glad you jumped in and shared your data experience with us. This is exactly the type of responses I'm looking for, in addition to driver perceived sound/reaction in a box after having done a recone job. I'm still searching on my side to find additionnal examples, and I will come back shortly with more info as it becomes available. All other recone/refoam examples are also welcomed, good or bad result , I don't care as long as we try to explain them to avoid other members a deception in reconing/refoaming driver X with recone kit Y ... Thanks again my friend !

Richard

[Flodstroem]

Hi to my Norwegian friends ! I worked for Norway's Kvaerner for many years in Canada... Richard

Thanks for your kind words Richard. In fact, I have Kvaerner-Stord, 10 minutes on the other side of our fjord here in Hardanger where I live

Regarding re-coning issues and to mix up different cone kits with not original baskets/magnet motors I would like to come back with an example
simulation later......

[RMC]

SECOND INSTALLMENT OF THREE, MORE INTERESTING THAN THE PREVIOUS ONE.

"Five parameters determine the driver's influence on response." (Bullock, p. 5) And he names the five has being: Re, Fs, Qes, Qms and Vas (here, that last one, is the one i'm interested in). "The remaining influences on response are..." Vb and Fb. Being a mathematician, Bullock probably has a mathematical model to explain why and how much the Vas parameter, linked to suspension compliance, influences the frequency response, but he didn't elaborate at this point. I assume it's related to the close relation of Vas with box volume...

John M. Eargle (JBL), Loudspeaker Handbook, Chapman & Hall, 1997, describes a driver's moving system as having 5 elements: cone, voice coil assembly, outer suspension (surround), inner suspension (spider) and dust dome. Then he writes "The purpose of the two suspensions is to ensure that the motion of the assembly is basically constrained to the axial dimension, with minimal radial and rocking motions. Each of these elements has a profound effect on the response of the driver,..." (p. 25). In his coverage of each item, he doesn't explain how/why/to what extent response is affected by the suspension (spider and surround).

In reality, the "original" suspension compliance parameter is Cms, but it is "translated" into a volume of air (the Vas parameter) "In order to help with this computation" (Alden, p. 16). Bullock adds "... Cms parameter is quite difficult to control in production. " (...) "For a particular driver model Mms is usually consistent from sample to sample but Cms is not. Thus Fs can vary quite a bit." "... formula 1 shows that a 50% compliance variation is possible."(p.9-10 Reader questions) "Cms not only varies quite a bit in production but is also hard to measure accurately."(p.10) Alden associates a driver's Cms with the "compliance of the spider and surround suspension system" (p. 16)

Regarding T/S parameter related to suspension, John Eargle writes: "The stiffness of surrounds and spiders may tend to vary to some degree, causing the Vas and Qts parameters to shift. The main question here may not be the variation itself, but the effect that variation may have on system performance. In most ported systems, the LF alignment is dominated by the enclosure parameters, and slight shifts in these parameters may have little practical effect." (p. 290) In relation to this parameter shift, "There is general accord that a 20% variation in Vas will not have serious effect on the final system response" (Alden, p. 17) This would mean larger shifts in Vas should have more extensive impact on performance.

With regards to determining Vas, Bullock writes "Vas is the most difficult parameter of all to find with acceptable accuracy. It varies not only with atmospheric conditions, but also with time..." Then interestingly adds "Luckily, this parameter's value is not as critical as the others: that is, a system's response will not be as sensitive to errors in Vas as it will to errors in the other parameters." (p. 14)

Bullock simulated (Fig. 5 & 6, p. 23) a ± 10% error in h (box tuning) and a ± 20% error in alpha (box volume), both for driver Qts 0.38 and box loss QL = 10, before concluding: "Notice that an error in alpha (box size) alters the response much less than one in h (box tuning). This state of affairs is desirable because Alpha = Vas/Vb and neither of these volume parameters can be measured with great precision." (p. 24) A 10% box tuning error has more impact on frequency response than a 20% box volume error...

Finally, he also simulated (Fig. 11, p. 24) a ± 20% error in Alpha (box volume) but this time with driver Qts 0.20 and box loss QL = 7. The changes in Alpha (box size) here also show a smaller effect on response compared to a ± 5% and ± 10% change in other parameters (Qts and h respectively). In fact, comparing his Fig. 6 and 11 with Fig. 8, his curves for Alpha changes/errors look more like those milder ones he simulated for the effect of box losses on response with QL 3, 10 and 15 (Fig. 8, p. 24). It does make sense since both QL and Alpha relate to box volume.

THIRD INSTALLMENT, INCLUDING CONCLUSIONS, EVEN MORE INTERESTING, TO COME SOON.

Richard

[RMC]

FIRST INSTALLMENT OF TWO, MAYBE THREE, AS THERE IS A LOT OF MATERIAL TO COVER HERE.

While adding Qts here (Barry measured Fs), the question I raised in the "2234 Butyl Surrounds from Japan" Thread in DIY Forum, in my May 15, 2017 post, was if the new surrounds had an impact on the Vas T/S para. used to determine box volume (Vb), possibly on box tuning (Fb), on low frequency response and Xmax.

In post #7 of Barry's Butyl Surrounds Thread, Ian stated "The T/L parameters have nothing to do with the suround," and "The surround minimises reflections back into the cone and provides air tight seal and centres the cone. Nothing else. In modern drivers a foam surround is not considered part of the radiating area."

That view appeared radical and sounded contrary to what I learned over many years. This prompted me to go back to my References. If the situation is such as described above, then the surround's role or impact is quite limited, similar to that of a "zombie following the parade", i.e. passively obeying to cone movement dictated by voice coil/spider. Moreover, it would imply any similar type surround which physically fits could be used successfully (I.e. with results equivalent to the original). That sounds too good and easy to be true I thought, in relation to my question "Did I wasted time and money in doing so..." in my previous post here.

For my part, I've always understood the surround had a more active contribution in a driver's suspension system (e.g. some restoring force along with spider and some part of radiating area).

I'm not sure I know what a "modern driver" is, in terms of year made, to fit the description but referring to a Nov. 1978 AES Preprint, Bullock (Bullock on boxes, 1991, p. 44) does write "The driver piston diameter is equal to the cone diameter plus two-thirds of the surround width." Regarding the measurement of effective cone diameter, David B. Weems says "To get the effective diameter, include the suspension (surround) on one side only with the measurement..." (Designing, Building, and Testing Your Own Speaker System, 4th edition,McGraw-Hill, 1997, p.140), and Ray Alden (also mathematician, like Bullock) adds "The surround also acts as part of this effective piston area, ... Including half the surround on each side of the cone as part of the "effective" diameter helps to approximate the true piston area." (Advanced Speaker Systems, 1995, p. 21) Could they all have it wrong ?

Concerning the other surround's role I mentioned as example, Stan Kelly describes it as: "The purpose of the suspensions (with s) is to provide a known restoring force to the diaphragm/voice coil assembly... " Rest of his phrase being as described by John Eargle below. " The combined stiffness of the front and rear suspensions are formulated to... " "The rear suspension is the major restoring force,..." Not the exclusive force. (Loudspeakers, in Audio & Hi-Fi Handbook, 2nd Ed., Ian R. Sinclair Editor, Newnes, 1995, p. 561-2)

Vance Dickason also says the surround "...provides a portion of the restoring force that keeps the coil in the gap." RE "The stiffness provided by the surround and spider..." "...the spider provides about 80 % and the surround perhaps 20 % of the total compliance." (The Loudspeaker Design Cookbook, 5th ed., 1995, p. 8-9)

SECOND INSTALLMENT TO FOLLOW TODAY (ALREADY WRITTEN).

Richard