Jantzen JA8008 alternatives

[Ed LaFontaine]

Zaph did test a pair of the JA8008.

Zaph|Audio

There appears in the Impedance plot a pair of peaks, circa 1K & 2K.

Are these anything to worry about?

Would there be a program of investigation leading to "treatments" to bring them under control?

I'm thinking this driver is better suited to an OB, ala Orion...

 

[LJNorth]

damping could be applied to the cone/change in surround - but that would result in what is essentially a driver already sold by seas for less that half the price. The difference in sensitivty, if you go by Zaphs measurements, would only be a couple of dBs anyway.

 

[bbggg]

a pair of peaks, circa 1K & 2K

They seem to correlate well with:

 

[academia50]

not wanting to repeat but the CA22RNY (the larger magnet version of the CA22 RNX) is about as close as you can get to the Jantzen without being a Jantzen - it is a solid 92 dB (only a couple of dB off the Jantzen) and less than half the price. It even has the same dip in response at 800 Hz and the same HF roll off. However any driver if it isnt the Jantzen will require a re-design. Is the effort worth the money?

I totally agree with LJNORTH.
I think there is no need to walk recalculating design the crossover to compensate for the difference in SPL. While there seems to be a lot of viewing the graphics, remember that + 3 db means half the power required ....
And yes, the driver of the Seas is that is most similar, because it was cast for Troels mainly changing the magnetic flux. It seems that was increased with more turns in the voice coil, Jantzen said it ..... but overlapping double coil? I do not think that the gap is the same ... seem larger number of turns in less space? Secret Troels and Seas.

I hope soon to receive my order. Now I will tell
Sorry mi english ....
Regards

 

[Celsius]

Looking a shop to buy the tweeter AUDAX TW034X0 I have found other alternatives to the woofer as Audax AUDAX HT210G2 can be it a good alternative? the curve of response a really interesting,

audax speaker units from cadaudio.dk

 

[academia50]

Looking a shop to buy the tweeter AUDAX TW034X0 I have found other alternatives to the woofer as Audax AUDAX HT210G2 can be it a good alternative? the curve of response a really interesting,

audax speaker units from cadaudio.dk

I have already received my kit DTWWTII and I chose the Audax tweteer TW034. Tweeter is originally selected by Troels, to engage the JA8008 network through appropriate junction. This is really important before changing any driver of a project.

Also, if you use the Audax HT210G2 for bass / midrange, the crossover no longer act alike.

Currently the JA8008 HMQ (new) can individually buy Jantzen Audio, but I repeat that it is necessary to redesign the crossover due to its high QTS


DTQWT-mkIII


Regards

 

[AlexanderTD]

It was interesting to read all the posts here. I have DTQWT (T35 variant) and also been thinking if Troels TL enclosures are optimal ever since i began to read MJK and other TL related sites. But my DTQWT measures actually pretty well, although i been thinking if it can be redesigned to a higher standard... So far i tried mass loading it (blocking half or more of the opening) and it result in more bass output and a bit less ripple in midrange so if anyone has DTQWT and want more bass - it's easy

Currently the JA8008 HMQ (new) can individually buy Jantzen Audio, but I repeat that it is necessary to redesign the crossover due to its high QTS

Sorry, just wanted to ask why you think QTS have changed? It's 0.25 vs 0.24 of previous driver and i actually was thinking why Troels say it need new crossover and can't be used with at least old T35 variant because freqency response is virtually the same as well as impedance...

 

[academia50]

Sorry, just wanted to ask why you think QTS have changed? It's 0.25 vs 0.24 of previous driver and i actually was thinking why Troels say it need new crossover and can't be used with at least old T35 variant because freqency response is virtually the same as well as impedance...

You are right, it was a mistake, I meant that the new driver JA8008 HMQ the qms (factor of merit due to mechanical losses) went from 1.7 to 10, so Troels has designed a totally new crossover network.

JA8008-HMQ

Troels said :
The aluminum voice coil former is now replaced by a fiber glass voice coil former with similar properties of e.g. Kapton and titanium. The result is an huge increase in Qm, actually I measure Qm = 10 from the driver samples fitted with a center phase plug.


If the above network crossing would have worked well with the new driver, you could not tell, my knowledge about it are not very large.
But you're right in thinking that ..... I'm a little disappointed with the change of controller, it seems the best driver that Troels manufactured (said by the same) is not anymore? I believe that business is business as usual.
Now it seems that a driver only , of 12 inches deeper than two of the 10 inch bass delivery, too ...

Anyway, I think the design of the rear of the MKIII to accommodate it, is simply ugly.: Eek:
So I'm working on DTQWTII with the same expectations, I will not pay psychologists to solve any trauma !! : D





What you mention to listen "more bass " by varying the load on the end of the horn, well, depends on individual taste .... I always prefer the reproduction is as flat as possible, that is, true to the original sound source



Sorry for my English.

Regards

 

[AlexanderTD]

You are right, it was a mistake, I meant that the new driver JA8008 HMQ the qms (factor of merit due to mechanical losses) went from 1.7 to 10, so Troels has designed a totally new crossover network.

I think Troels just redesigned the driver AND also decided to try a new crossover. He moved to "stepped" baffle a long time ago and liked LR2. But i don't think it's because new driver required it. And personally i like older T35 first-order (electrical) crossover more. I was thinking to just replace the driver with new one without changing the crossover...

But you're right in thinking that ..... I'm a little disappointed with the change of controller, it seems the best driver that Troels manufactured (said by the same) is not anymore? I believe that business is business as usual.
Now it seems that a driver only , of 12 inches deeper than two of the 10 inch bass delivery, too ...

Why you say that? I like high Qms drivers! I think the JA8008 just got better, a little. And i like that shiny bullet Otherwise they are VERY similar, the main difference is voice coil former (which result in different QMS) and phase plug plus slightly larger magnet and that's it, same driver otherwise!

What you mention to listen "more bass " by varying the load on the end of the horn, well, depends on individual taste .... I always prefer the reproduction is as flat as possible, that is, true to the original sound source

By mass loading you lower tuning frequency and allow for deeper bass so = more flatter and true to the source i guess. This way you can get as low as single 12" in MKIII which goes deeper probably because of lower Fs which is important despite what Troels says. I have Beyma SM-110 drivers which Troels used before Eminence and they go deeper because of lower Fs.

In any case - if you're just building these speakers prepare for a long burn-in time and don't judge bass before month or two. These are incredible speakers and JA8008 is one of best midranges i ever heard (and i have accuton and scanspeak to compare to)

 

[pk]

JA8008 vs. Accuton

Hi Alexander,

Having compared the JA8008 (the new HMQ version?) to the Accuton drivers, do you think the JA8008 has the same clarity in the mids as the Accutons?

Thanks a lot!

Best regards
Peter

In any case - if you're just building these speakers prepare for a long burn-in time and don't judge bass before month or two. These are incredible speakers and JA8008 is one of best midranges i ever heard (and i have accuton and scanspeak to compare to)

 

[AlexanderTD]

Hi Alexander,

Having compared the JA8008 (the new HMQ version?) to the Accuton drivers, do you think the JA8008 has the same clarity in the mids as the Accutons?

Thanks a lot!

I have older JA8008 for now. But it is very fast, dynamic and detailed for 8" while smooth at the same time. It is capable of producing "bite" and attack even at midrange which feels more "relaxed" with regular drivers. JA8008 and DTQWT speaker is pretty much just like a good single driver speaker, but without limitations in bass and treble.
Accutons I listen to are in Tony Gee Soup Sandwich speakers so not 100% accuton sound, only midrange and tweet, but my impression is that accutons are very precise and uncolored - their sound feels "crystal clear", but sometimes i feel there's slight "edge" to them like when you switch from soft dome tweeters to hard domes, like they give you a taste of material they are made of, although to a slight degree. And they also never impressed me as being terribly dynamic. But maybe it's more efficiency related...

 

[academia50]

AlexanderTD :

I know the subject of the break in the ja8008. I think one of the reasons for the new release, is in the phrase when he says Troels not notice any change in the new driver, ie, no alteration of the compliancia after many hours of use ...
The recommendation to soften hands suspensions has brought with it many broken cones .... someone who has a minimum of knowledge and gently with your hands can wreak havoc in an effort to shorten the time of shooting.
Let's face it, it's too long to wait 400 hours of use (which recommended) for a driver down the FS and only then work as expected ..... because if there is loss of mechanical elasticity at that time, who ensures that stabilizes and does not follow loosening indefinitely to resemble a driver for sealed box?
And as to whether the same would use the old crossover ...... then look at this and understand why I am concerned that is discontinued .... few JA8008 will Jantzen Audio in its stock for this kind of problem? ??? And it is not because, once again, that by Troels, use the old crossover.
Maybe that's the reason to produce massively by HMQ Seas, could now have original repair kits .... but I can not tell.
We will have to take good care of our driverJA8008.
As I have gone through some bad experiences (with official representatives of JBL, for example), I do not trust repairs without original parts, never work the same although local repairmen speakers ensure otherwise.

DTQWT-Andrey

Regards

 

[pk]

Hi Alexander,

Thanks a lot for your reply!

Best regards
Peter

I have older JA8008 for now. But it is very fast, dynamic and detailed for 8" while smooth at the same time. It is capable of producing "bite" and attack even at midrange which feels more "relaxed" with regular drivers. JA8008 and DTQWT speaker is pretty much just like a good single driver speaker, but without limitations in bass and treble.
Accutons I listen to are in Tony Gee Soup Sandwich speakers so not 100% accuton sound, only midrange and tweet, but my impression is that accutons are very precise and uncolored - their sound feels "crystal clear", but sometimes i feel there's slight "edge" to them like when you switch from soft dome tweeters to hard domes, like they give you a taste of material they are made of, although to a slight degree. And they also never impressed me as being terribly dynamic. But maybe it's more efficiency related...

 

[matejsirk]

I have one pair of JA8008 (new-unopen) for sale, cos I cancel the project. If somebody is interested... Contact me on PM.

 

[NicB]

It was interesting to read all the posts here. I have DTQWT (T35 variant) and also been thinking if Troels TL enclosures are optimal ever since i began to read MJK and other TL related sites. But my DTQWT measures actually pretty well, although i been thinking if it can be redesigned to a higher standard... So far i tried mass loading it (blocking half or more of the opening) and it result in more bass output and a bit less ripple in midrange so if anyone has DTQWT and want more bass - it's easy

Hi AlexanderTD,

Sorry if this is off-topic, I am finishing a pair of DTQWT at present. What did you use to block the opening?

Cheers,

Nic

 

[AlexanderTD]

academia50, i think new JA8008 should work in place of old one. QTS is the same, response is the same, impedance is the same... What else we need? And Troels is working on new crossover for dual 10" cabinets, but it won't surprise me if he just writes one day "just plug the new driver into DTQWT MK2 and be happy"

Sorry if this is off-topic, I am finishing a pair of DTQWT at present. What did you use to block the opening?

I simply used large books of different sizes for experiments and put them under the speaker so they block half or more of the opening depending on book size. You can also use adjustable feet but you need to set height real low to see significant change. The idea is to reduce opening to area less than opening so that it loads the speaker.

Here's measurement of how blocking about 1/2 of the port affect it's output (port output only).

 

[NicB]

academia50 I simply used large books of different sizes for experiments and put them under the speaker so they block half or more of the opening depending on book size. You can also use adjustable feet but you need to set height real low to see significant change. The idea is to reduce opening to area less than opening so that it loads the speaker.

Thanks for your reply AlexanderTD. I will give this a try once the speakers are going... hopefully one week away!

Nic

 

[academia50]

academia50, i think new JA8008 should work in place of old one. QTS is the same, response is the same, impedance is the same... What else we need? And Troels is working on new crossover for dual 10" cabinets, but it won't surprise me if he just writes one day "just plug the new driver into DTQWT MK2 and be happy"

Alexander, I mentioned that the Qms is very different. The magnetic flux (Gauss) of the voice coil is greater, all influences. Different damping in the new driver (compliancia) requires redesign the crossover. If you put the new driver HMQ in the old frequency divider surely measurements are not equal. Also remember that having bass drivers in the rear panel, measurements are difficult, as you said Troels. Recommends keeping the high impedance (6 ohms minimum working) DTQWTIII if used with a SET amplifier, and using 2 x 10 inch Eminence. He also mentions that the vast majority of builders use DTQWTII solid state amplifiers (SS) Maybe that's the reason for using 1 x 12 inch Eminence, we can not know exactly, but I trust the seriousness of Troels as a designer. I hope I never need to replace the old JA8008!

Regards

 

[AlexanderTD]

Yesterday i studied response and impedance plots closely and i realized that Troels is right when he says old crossover won't work without changes. The answer i think is not as much in frequency response differences but more in impedance plot - new 8008 has small "fluctuation" around 800hz which likely results in more pronounced dip/peak combo when crossover is used, hence LCR circtuit to tame it. Should be less of a problem for T35 variant though as it's crossover point is lower
T35 variant definitely has a better chance of using HMQ driver without changes to the crossover, maybe with LCR circuit. I could give it a try since i have T35 variant, but i guess it's easier to wait until Troels come up with a new crossover for dual 10" DTQWT.

academia50, QMS by itself doesn't affect how crossover works, only total QTS which is the same. The only reason new driver "won't work" with old crossover is minor differences in impedance and frequency response which will result in larger peaks/dips in crossover region making it less optimal. For non-T35 DTQWT at least. I believe i can make it work with my T35 variant, maybe with additional LCR circuit.

As for bass drivers - 12" is just cheaper than two 10" and maybe will go a bit lower, but two 10" will have more impact in upper bass. But any DTQWT has plenty of bass if tuned(stuffed) right.

P.S. if you don't want to replace your JA8008 then don't, what's the problem? I want to try new driver but i'm not sure i like new crossover or cabinets. I like T35 variant the best

 

[snup]

I have been waiting for the OBL15. I guess Troels has issues.