woofers 4425

[alpina]

The 2206h is best that 2214h,yes.. But I have sold it for some time.
I have decided, without haste but without pause, to buy your used or new 2214h ... I will see. I have enough music to listen on my other devices and it is always more profitable to sell with original components in the supposed case.
I'm also thinking about another project to do at home ... and as they say, rushes are not good !. Anyway, I have saved the suggestions written here as they come in handy for those other projects. From here, my total gratitude.

[RMC]

Hi Alpina,

RE: "The 2206H is best"

Best for what purpose? Every driver is developed with an intended use in mind. The 2206H was optimized for high power/level sound reinforcement, whereas the 2214H was optimized for high fidelity/studio monitoring purpose in mind. These are two different ball games. Sure a 2206H would still produce sound when used in a 4425 cabinet, maybe even acceptable sound to some, but it was not optimized for critical listening in a studio monitoring environment or for home high fidelity as the 2214H.

Because the 2206H has the JBL name on it and its baffle cutout is 280 mm VS 281-2 mm for 2214H its an appealing and convenient drop in easy fix, physically speaking. But there's a lot more to it than that. Appearance wise, the 2206H's cloth surround, 4" voice coil/dustcap and cone depth betray the woofer's non-original status.

On the technical side, though some of the 2206H electrical parameters (e.g. LE, RE) seem acceptable, some of the important box related parameters are not even close to those of a 2214H: Fs 52 hz (23hz), Qts 0.32 (0.24), Vas 62 L (224 L); sensitivity 95 db (91 db), a notable 4 db difference which would put the 2206H sound forward compared to the rest of the 4425 system.

In the 2206H spec sheet the suggested box is Vb 57 L /Fb 50 hz. In the 4425 spec sheet using 2214H the box has Vb 53.8 L/Fb 34 hz. The 2206H box has a little larger volume but a MUCH higher tuning frequency and an F3 at 50 hz, so forget about low bass in that case...

My initial impression was that dropping in a 2206H in a 4425 box would likely yield a small bass bump because of higher driver Qts and a little smaller box volume. But then the combined effect of much lower box tuning frequency of the 4425 would also kick in creating a dropping low frequency response.

So I've modeled quickly the 2206H in Winspeakerz software with the 4425 box parameters given above. The result is poor, as expected, with a pretty dropping response in the low end (from 150 hz down), unless one would use 2-3 boundary box placement: -5db/50hz, -7db/40hz, etc. Morever, above 150 hz the response is at +2db. How do you think this box would sound? Likely weak bass, strong low-mid and a general driver level higher than it should in view of its 95 db sensitivity VS 2214H/4425 91 db.

Re-tuning the box higher for better 2206H driver performance in that box would imply shorter vent tube and/or increasing vent diameter, the latter not a practical change to revert back to the previous situation, specially with particle board.

That being said, I don't necessarily agree with an earlier statement made here that an increase in baffle cutout (and/or vent area) is non-reversible (across the board). I've done it a couple of times with success to avoid scrapping good boxes. But then ALL my speaker builder boxes are made of plywood for a number of reasons...

Richard

[Ian Mackenzie]

http://www.audioheritage.org/vbullet...12-quot-Woofer


https://reconingspeakers.com/product...2g-12-speaker/

Apart from being a 4 ohm driver it’s an excellent driver as used in the LSR 12 inch system

Some basic re design of the low frequency network and you are done

[johnlcnm]

RMC. I agree with your analysis of the 2214 and 2206 parameters. The 4425 ports are tuned to 40Hz. The measurement plot shows a check mark response down to 40Hz, which was expected. 50Hz would probably give a flatter response, but I do have a 60Hz resonance in my room which seems to counteract the lull at 60Hz. I will have to look for the waterfall bass response plot. I did kill the LF section of the existing crossover network and build a separate LF network for the 2206. Could use more work/experimentation at this point for sure. I never thought of using the 252G. Could have been purchased maybe for the same price as the 2206s I obtained.4425NewWoofSum.pdf

[Ian Mackenzie]

The 4425 was tuned to 34 hertz

See page 2 in this link

http://www.jblpro.com/pub/recording/4425.pdf

[johnlcnm]

My measurement. I think I made the measurement with the 2206s. Could be the volume difference between the 2214 and 2206, or cal error in my equipment.

[Ian Mackenzie]

No worries.

The 1200H used in the Century Gold (1.8 cuft3) is tuned to 32 hertz.

[johnlcnm]

I went though quite a journey with the 4425's. They had a resonance somewhere around 2kH to 3kH. I replaced the high frequency compression drivers with the commercial 2426H's loaded with new Radian diaphragms. Did not solve the resonance issue in the upper midrange. The problem was the 2214H's. Replacing them with the 2206H's solved the problem. Also improved the midrange considerably. IMHO the 1200Hz crossover is a little high for the 2214H's. Their first breakup mode is just too close to that crossover frequency.

No doubt the 1200FE-8 is a much better driver then the 2214 or the 2206 for a small home system. I also have the 4429's in my main system. The 1200FE-8 not only has excellent bass, but a very good lower midrange. My fav. JBL 12 incher. A really great driver.

[RMC]

Hi John,

RE: The 4425 ports are tuned to 40Hz; Could be the volume difference between the 2214 and 2206


I don't see how a new and original 4425 box could be off this much (Fb 40 hz VS 34 hz or 18% more) from the factory, unless they installed wrong tube(s) lenght ? Do both boxes have the same Fb 40 hz?

However, If the boxes were purchased used, could be a possibility a previous owner replaced or even shortened the vents to re-tune the box higher for better performance with a driver different than original? Have you checked/feeled the tubes' cut at the inside end of the boxes to confirm a smooth as a machine made factory cut or can you feel with finger(s) some signs of another tube cut made? Do vent tubes have all the same length?

Checking the low-frequency impedance curve of the 4425 in the original spec sheet dated 01/86 and in the subsequent one 7/93 (to assess if Fb 34 hz a typo?), confirms the minimum impedance point between the two LF impedance bumps appears located at the right place on the graphs. So 34hz doesn't seem a typo.

JBL 12" drivers from that period of time are regularly described as having a "volume displaced by driver" of 4 L. or 0.15 cu.ft. I don't see where the 2214H and 2206H can be so different in size so as to explain such a shift in box tuning frequency from the expected 34 hz to 40 hz. I assume a tolerance of a few hz is acceptable.

Another way of looking at this driver volume displaced issue and its effect on Vb/Fb could be the following. According to Electro-Voice, box volume "Variations of + or - 5% of the specified net internal volume will not materially affect performance." (Pro Sound Facts, No. 7, Oct. 1984, P. 7) I tend to think the shift from Fb 34 hz to 40 hz is material, more so in the context of a studio monitor/critical listening application for example.

On the other hand, the net box volume of the 4425 is 53.8 L., so 5% of that volume = 2.7 L. or so of tolerance. And we know the volume displaced by JBL 12" drivers of that era is of the order of 4 L. as per "JBL: Conversion constants and Useful Data", along with some data sheets: e.g. 2206H, 2204H, 2202H.

Therefore, this would mean box performance is materially affected when greater than 2.7 L. or so, on top of the 4 L. or so already factored into Vb, is in effect: 4 L. + 2.7 L. = 6.7 L. Is the 2206H, or the 2214H for that matter, that much larger (6.7/4 = 68%) than the other? In my book that's a NO. Even more so knowing the volume displaced by a 15" driver of similar era is 6 L. based on JBL data... Even putting the 2206H at a fat 6 L. (which is not real), it wouldn't justify the Fb shift here, and that's the volume taken in the box by a 15"!

Driver size difference mentioned here, and its possible effect on Vb/Fb, a feasible explanation re tuning frequency shift? It sure doesn't appear to be the likely reason in this case. If vent(s) modification doesn't explain it, then measurement method or calculation error would seem to be the likely cause among those mentioned. Regards,

Richard

P.S. Another possible cause could be more than usual box losses (QL) and their impact on effective box Vb, and by rebound on Fb? This could also be part of the explanation...

EDIT: Regarding the above P. S. note.

RE:"I did kill the LF section of the existing crossover network and build a separate LF network for the 2206."

"2214H's. Replacing them with the 2206H's"

"I replaced the high frequency compression drivers with the commercial 2426H's loaded with new Radian diaphragms"

The original compression driver of the 4425 is 2416H as per JBL Data Sheet and Technical Manual.

With all due respect, considering all these changes made to the system what you really have is sort of a "Frankenstein" 4425 system. This gives me the impression that in the making maybe the original box air tightness has been somewhat compromised?

For sure an Fb 40 hz gives a little better response with a 2206H in a 4425 box (vs Fb 34hz), but still short from an Fb 50+ hz in terms of response flatness, as seen in Winspeakers modeling software.

[johnlcnm]

Richard,
It has been a while since I made that measurement. It was definitely a small signal measurement. 100 Ohm resistor in series with the signal generator, and VOM across the speaker input. I guess that would be referred to as a down and dirty measurement. I am going to make that measurement again. This time no resistor and through an amp. I'll feel for cone movement. Will report back! At the time I had the data sheet, but didn't look for the box resonance. I know that a small signal measurement can be different then a large signal measurement.

Regards,

John