New Jamo dipole

[Jonasz]

Have you guys seen this? 8O

I'm happy to see more commercial dipole speakers! :P Could it be a Revelator tweeter with Seas Excel mid and SLS 15" woofers?

More info here: http://www.jamo.com/Default.asp?ID=2...roductID=17625

Jonas

[TacoD]

I also agree on the tweeter 71000, (looking at the back of the tweet). Very nice styling.

[JonMarsh]

And, uh, technically, this is a Klipsch diople speaker, as Jamo is wholely owned by Klipsch... weird, huh?

~Jon

[Paul H]

Interesting. At one point in my 'little dipole project' I was looking at 2 15"drivers and a single 6.5" mid, but concluded that it was too much of a stretch for the 15" drivers to 'reach up' to the 6.5". With the beaming and distortion from 15" drivers at higher frequencies, and the difficulty of getting lower frequencies from a single mid in a dipole setup I just didn't expect it would work really well.

I'm kind of sceptical about the magnesium driver without breakup until 9 kHz, and the baffle width looks kind of small to get meaningful bass without very extensive crossover/boosting, but nevertheless I'd love to hear these.

Paul

[JonMarsh]

Well, after what we did with the Whisper Klones (two compound 15" drivers per panel) I'd say it's doable, maybe with only some passive EQ, and nothing but passive above 100 Hz. BUT, that design used 4 7" midwoofers- OTOH, they were Etons, which don't have the most remarkable motors. The multiplicity was for getting dispersion control...

Still, it's interesting, and would probably be interesting to hear...

How about an RS series based Klone, with maybe three 12's, an RS180, and H1212? Sort of like a spin off of the Gradient Revolution, only different...

[Dennis H]

One nice thing about pro 15" or 18" drivers is most of them have light cones. Couple that with the big Sd (shorter stroke required) and you can move quite a bit of air without a whole lot of the mechanical vibration that plagues big dipoles.

[AJINFLA]

Yup, I'm with you on that one Dennis. If I were to go that route I'd probably use these: http://www.ciare.com/oem/pdf/1800NDW1.pdf



cheers,

AJ

[Doug Lockwood]

"And, uh, technically, this is a Klipsch diople speaker, as Jamo is wholely owned by Klipsch... weird, huh?"

Is a dipoles a form of waveguide?
Isn't a waveguide a horn? :rofl:

Sorry, couldn't resist.

Doug

[JohnL]

I like the bar going up the back, I wonder where they got that idea?? :roll:

AJ - Didn't Magnatar make some reference about hi-efficiency (pro-sound style) woofs not working well in a dipole? I don't remember why, but I think he tried OB with a couple of Audax PR330s and ended up sticking them in a box (or a horn or karlson or something). Would there be any reason you can think of that they wouldn't work well? ...or at least as well as a couple XLSs or TC2s or something?

[JonMarsh]

Dipoles work best with woofers with moderate to higher Qts (say, 0.4 to 0.7), and most pro sound woofers are designed for efficiency with big magnets, high BL product, low Qes, and low Qts. I used some Audax Pro 15s and 13s in my X1 Klones, and they had a Qts around 0.22.

[AJINFLA]

Hi John,

um, you mean Magnetar who called OB "Linkwitz distortion boxes" (his words)? The same Magnetar that touted his great "discovery" of a new type of dipole (I jokingly called it the "Magnapole" ), only to be corrected by John K, that it was all rubbish. THAT Magnetar? LOL. The dude is ensconced in a world of delusion in his basement.
Karlsons are the ultimate :rf if you listen to him.
Karlsons 8O :rofl: !!! Nuff said.
Dipoles need to move air. LOTS o' air. Sd. Xmax. Low distortion. Low excursion noise. That could be a home, pro or car driver. Take yer pick.

cheers,

AJ

[AJINFLA]

Jon,

while I certainly agree with you that the higher Q drivers are easier to work with, there is no reason why the lower Q drivers can't be used. SL explains this on his site. Remember that the XL's have low Q's due to their strong motors and SL uses them just fine.


Q - What is the optimum Qts for the drivers of a dipole woofer?

A - The low frequency roll-off of a woofer and its associated group delay are optimal, from what I have observed, when they follow the response of a 2nd order highpass filter with Q = 0.5. When a driver is mounted in a dipole W-frame or H-frame its mechanical resonance frequency Fs decreases to Fd, due to air mass loading, and Qts increases by a similar percentage to Qtd.
For example, a driver with very strong motor, Fs = 18 Hz and Qts = 0.2 might have Fd = 16 Hz and Qtd = 0.22 as determined from an impedance measurement of the baffle mounted driver. With Qtd < 0.5 the low frequency behavior of the woofer is characterized in the complex s-plane by real axis poles at -69 Hz and -3.7 Hz and by 3 zeros at the origin. One of these zeros is due to the front-to-back dipole cancellation with its 6 dB/oct low frequency roll-off. The frequency response of this 3rd order acoustic highpass filter must be equalized to obtain a flat response. A suitable target response could be Fd = 20 Hz and Qtb = 0.5. It is easily realized with two shelving lowpass filters. The first filter with a pole at 20 Hz and a zero at 69 Hz corrects for the low Qts of the driver. The second filter with a pole at 20 Hz and a zero at 400 Hz compensates the 6 dB/oct roll-off due to dipole cancellation. The 3.7 Hz pole is low enough in frequency so that the response is dominated by the 2nd order roll-off below 20 Hz. An advantage of a low Qts driver is the ease with which it can be equalized for an optimum response with Q = 0.5.
A driver with a smaller motor might give Qtd = 0.7 and Fd = 20 Hz, which leads to a pair of complex poles in the s-plane. This can be readily changed to a 3rd order Bessel highpass response by using a shelving lowpass filter with a pole at 20 Hz for the necessary dipole roll-off compensation.
Likewise, if Qtd = 1 and Fd = 20 Hz, then an additional pole at 20 Hz, from the dipole equalization, leads to a 3rd order Butterworth acoustic highpass response. Third order filters introduce more group delay than 2nd order ones. It is therefore advantageous to use Qts < 0.5 drivers, even when they require driver roll-off equalization in addition to the normal 6 dB/oct dipole correction.


cheers,

AJ

[Dennis H]

Those look pretty nice, AJ. They don't seem to have the breakup around 300Hz that a lot of the big pro drivers show. Where can you buy them an how much?

[AJINFLA]

BTW,

the 71000 is my dream tweeter :drool: .
Some SOB in Italy outbid me on ebay, at the last sec, for a pair :M .
I hate it when that happens .

cheers,

AJ

[AJINFLA]

Hi Dennis,

I found them here: http://www.assistanceaudio.com/08_CIARE.html#neo
Quite reasonable IMHO. I like the small rear structure for dipole use.
Ciare seems to have a good rep. Perhaps others can shed some light.
The other Pro driver I like in that price range is this: http://www.partsexpress.com/pe/showd...number=294-301
Opinions on that one seem to vary widely amongst the Pro crowd.
The Xmax and Le 0.87 8O has caught my eye. The rear vent looks quite large.
Trying to hide those from the wife may be a whole other story.
But honey, I only need 2 per side so the cabinets can be sooo shallow....

See why I'm divorced :W .

Cheers,

AJ

[Dennis H]

Yeah, I've looked at the Peavey but I've never heard one. FWIW, Jon Risch works for Peavey and says that's a really nice driver. He said it's pistonic to at least 300 Hz but he didn't know beyond that. One problem is the Mms is a bit high but it's not terrible. Another nice looking pro driver is the Eminence Magnum 15 LF. It's one of the few where they publish an X10 spec (X for 10% distortion) and it's well beyond the nominal Xmax.

http://editweb.iglou.com/eminence/eminence/pages/products02/pdf/magnum.pdf

[AJINFLA]

Hmmm, the Magnum seems to be the same price as the Kilomax :scratchhead: .

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-434

Both are about 3 bills. The Peavey may be the better value at less than 2. The Ciare might be the SQ champ and its about 2 as well.
All of them are quite large :B
I like.

cheers,

AJ

[JohnL]

3 zeros in the origin? That's why I post here; every time I think I have a handle on speaker design, somebody pops up with a post like that, that I read 5 times and have no clue what it means. ;x(
I got the basic concept, but the math eludes me.

In any event, regarding Magnetar. I was unaware of any past foibles of his. I understand he was banned from AA, but I didn't know the details. I saw some of his designs and they seemed interesting, he seems to be into old-tech, hi-eff stuff, which can be cool. He caught my eye because of his use of AMTs, which I honestly think are the holy grail of high frequency reproduction. I guess I'm just still at the point in this hobby where I'm trying to take input from everyone and see what works for me (Like cauer-elliptical filters). :T

John

[JonMarsh]

Jon,

while I certainly agree with you that the higher Q drivers are easier to work with, there is no reason why the lower Q drivers can't be used. SL explains this on his site. Remember that the XL's have low Q's due to their strong motors and SL uses them just fine.


Q - What is the optimum Qts for the drivers of a dipole woofer?

A - The low frequency roll-off of a woofer and its associated group delay are optimal, from what I have observed, when they follow the response of a 2nd order highpass filter with Q = 0.5. When a driver is mounted in a dipole W-frame or H-frame its mechanical resonance frequency Fs decreases to Fd, due to air mass loading, and Qts increases by a similar percentage to Qtd.
For example, a driver with very strong motor, Fs = 18 Hz and Qts = 0.2 might have Fd = 16 Hz and Qtd = 0.22 as determined from an impedance measurement of the baffle mounted driver. With Qtd < 0.5 the low frequency behavior of the woofer is characterized in the complex s-plane by real axis poles at -69 Hz and -3.7 Hz and by 3 zeros at the origin. One of these zeros is due to the front-to-back dipole cancellation with its 6 dB/oct low frequency roll-off. The frequency response of this 3rd order acoustic highpass filter must be equalized to obtain a flat response. A suitable target response could be Fd = 20 Hz and Qtb = 0.5. It is easily realized with two shelving lowpass filters. The first filter with a pole at 20 Hz and a zero at 69 Hz corrects for the low Qts of the driver. The second filter with a pole at 20 Hz and a zero at 400 Hz compensates the 6 dB/oct roll-off due to dipole cancellation. The 3.7 Hz pole is low enough in frequency so that the response is dominated by the 2nd order roll-off below 20 Hz. An advantage of a low Qts driver is the ease with which it can be equalized for an optimum response with Q = 0.5.
A driver with a smaller motor might give Qtd = 0.7 and Fd = 20 Hz, which leads to a pair of complex poles in the s-plane. This can be readily changed to a 3rd order Bessel highpass response by using a shelving lowpass filter with a pole at 20 Hz for the necessary dipole roll-off compensation.
Likewise, if Qtd = 1 and Fd = 20 Hz, then an additional pole at 20 Hz, from the dipole equalization, leads to a 3rd order Butterworth acoustic highpass response. Third order filters introduce more group delay than 2nd order ones. It is therefore advantageous to use Qts < 0.5 drivers, even when they require driver roll-off equalization in addition to the normal 6 dB/oct dipole correction.


cheers,

AJ

You and SL are correct, BUT, he asked why Pro sound drivers don't work well in dipoles, and that is exactly why they don't. Another factor is that Pro sound drivers have a rather low Cms typically, and high Fs. Take a look at the electrical equalization required to get a 0.22 Qts driver up in the bottom end- and look at Linkwitz's own comparison between moderate and low Q drivers in Dipoles and why he made the design recommendations he did. I don't particularly advocate Qts of 0.7; what I do advocate is around 0.4 to 0.45. Many Pro sound drivers actually have a Qts under 0.2- the Audax 15's, for example, at 0.18. That requires a considerable amount of equalization to pull into the ball park, where as using drivers in the range I prefer will often yeild pretty reasonable results with as little as 6-8 dB boost, which is feasible to do passively.

Being the luddite I am, I'm not big on using an elaborately designed preamp with top tier cables and then sticking a bunch of opamps in the signal path.

~Jon

[cjd]

Being the luddite I am, I'm not big on using an elaborately designed preamp with top tier cables and then sticking a bunch of opamps in the signal path.

How recently have you messed with sticking a bunch of op-amps in the signal path? Or rather, how recent were the op-amps? Just a curiousity at this point - my liking for op-amps is their bland simplicity - even *I* can whip up circuits with them and be moderately successful. :P But the sound is still pretty darned good.

For dipole I was thinking more along the lines of a few 15's (or 12's perhaps), a few 8's, a couple planars and a ribbon or planar to round it out... maybe 12's, 7's, would work better than 15's and 8's?

C

[AJINFLA]

No Jon,

YOU are correct . Most pro drivers are unsuitable for dipole use. However, recently there have been a newer wave of drivers that are quite suitable. It seems that some of the pro manufacturers are catching on for the need for larger Xmax "sub" bass drivers. Look at the specs on the 2 I have sited. There are others as well. Lower Fs (below 30 for both), reasonable Xmax, etc. Yes the very strong motors often give them low Qts, but again its not insurmountable. Those are the ones I was referring to.

Cheers,

AJ

[ThomasW]

How recently have you messed with sticking a bunch of op-amps in the signal path? Or rather, how recent were the op-amps? Just a curiousity at this point - my liking for op-amps is their bland simplicity - even *I* can whip up circuits with them and be moderately successful. But the sound is still pretty darned good.

Op-amps haven't changed all that much in the last 5yrs or so. Burr-Brown stuff pretty much defines state-of-the art, and I assure Jon knows these things inside-out, upside-down, backwards, forwards, and any other direction you can name.. Since his profession deals specifically with semi-conductors, he's got most aspects of this field pretty well covered..... :wink:

He prefers discrete devices and having no global negative feedback in the signal path.... :T

[JoshK]

JohnL,

Don't feel bad that the math eludes you in SL's posts. It often eludes me too and I have a masters in applied math. I couldn't grasp what he was talking about without doing some research into how the system is being described mathematically and then working through the math myself. Then again my math education was quite a bit different than typical math programs (more statistics, economics & physics related).

The problem with some of SL's posts on his site is that the are not self contained. He is walking the tight rope of trying to be intuitive and understandeable, while still being "correct" and rigorous enough for his engineering colleagues. Sometimes I think he misses both marks as a result, but most often he does a really nice job of balancing.

For instance, I have little intuition in why complex space is needed to describe this physical system. My FIL who is an EE, says the greatest disservice mathematicians every did to the field of engineering was using complex analysis to describe was is fairly intuitive. The math of complex space isn't hard, but the intuition sometimes fails me. Then again, most math programs spend little time trying to teach intuition.

In short, just know that zeros, in the context that SL uses usually mean solutions.

[cjd]

Op-amps haven't changed all that much in the last 5yrs or so.

I've heard some that would disagree with that (and think that there HAS been progress in the last 5 years particularly), but really have no personal basis for belief. I knew Jon worked with this stuff, just wasn't sure if he bothers trying anything any more in audio.

I prefer live music, but. . .

[DIY_newbie]

No Jon,

YOU are correct . Most pro drivers are unsuitable for dipole use. However, recently there have been a newer wave of drivers that are quite suitable. It seems that some of the pro manufacturers are catching on for the need for larger Xmax "sub" bass drivers. Look at the specs on the 2 I have sited. There are others as well. Lower Fs (below 30 for both), reasonable Xmax, etc. Yes the very strong motors often give them low Qts, but again its not insurmountable. Those are the ones I was referring to.

Cheers,

AJ

AJ,

I agree with you for the most part, however I think people place way too much emphasis on x-max for dipole use. I tried a pair of long throw woofers in my h-frame originally and wasn't really impressed.

I ended up using a pair of high sensativity 12" woofers (93 db @ 2.83v - 8 ohm nom) so the rated sensativity of the two drivers in parallel is 99 db @ 2.83v - 4ohm nom) Their low FS 25hz, mid Q .42, and high vas 8.4 CF was perfect for a dipole.. I sized my H-frame such that roll-off started at around 160 hz. Adding a low pass filter at 40hz. Leaves me flat at -12db from 40 -> 160. 99 db/2.83v at -12fb = 87db efficient for the system.. Thats better than most long throw sealed box woofers

I ended up EQing them flat from 20hz, and even with their limited x-max (2.25mm) they don't even come close to running out at normal listening levels.. As soon as I get a chance I'll post some pics on a new thread here and I look forward to seeing pictures of your project!

Best Regards

--Chris

[ThomasW]

I knew Jon worked with this stuff, just wasn't sure if he bothers trying anything any more in audio.

I prefer live music, but. .

The second time I met Jon in the very late 1960's, his band was performing at an outdoor concert. He was singing, playing flute, and his 'portable' Hammond B3, while doing the live mix...... 8O

Jon stays up to speed on all types of audio related semiconductors. At this point the preferred dual op-amps are BB OPA-2604 or 6123's

[JonMarsh]

There's a few newer and more "exotic" things, too, like the AD826.

But overall, for an inline equzlizer, I'd prefer something passive, or with no gain, just a simple buffer with high linearity (not an opamp configured as a buffer).

I used to like the old BUF-01's when they were available (I have a large stash), and the amplifier and preamp circuits I play around with are all non-loop feedback designs- comes from my past experience with Ayre, and ownership of Ayre gear. Another good brand in that regard is Theta digital. Integrated opamps are a lot easier to work with, on the surface, than discrete digital, but to get as good a sound as they're capable of still requires some care in layout, shielding and groundig, and bypass, as well as passive component selection. Different brands of resistors don't sound the same, IMO. It multiplies from there when you get into capacitors and the like....

~Jon

[AJINFLA]

Hi Chris,

don't laugh too much, but here is my "website" with pics. As you will see its not really a website, but a dumping ground for what little documentation I have of my most recent projects - pictures! I've been fiddling around with audio and computers for a long while, but the thought of keeping an organized journal of anything never even crossed my mind. Its not until recently joining these message boards and reading sites like Zaphs, etc, where I see that there are some smart folks out there that are really taking the time to document what it is they are doing so that it can be shared with others, What a concept .
However, with my limited time to do stuff with speakers, the choice between just doing it (building/testing,etc.) or taking the extra time to document, organize and post coherent info on a website, always seems to slant towards just doing it! Hopefully down the road I will have the time and circumstances to reverse this.

As far as using drivers like the ones you chose, the only real issue would be max spl. You can obviously eq any (just about) woofer down to 20hz, but your spl level will be highly dependent on xmax, especially at 20hz!
I think sometimes we get at little too caught up in high requirements for levels at 20hz, where very little music resides, quite dependent on what you listen to. But as the old saying goes - its better to have it and not need it than to need it and not have it. If you're even nearing Xmax, your distortion levels are rising.
I have bottomed my H-frame XLS 12's at high spl before, which is why I use ServoSubs below 40hz - on occasion. Those occasions are exceedingly rare given my living situation. It really only happens when I demo the main rig (much to my neighbors delight :W )

Cheers,

AJ

http://www.openbafflespeakers.com

[Victor]

Those Jamos do look good. Before I built mine, I actually considered a similar configuration, but ended up preferring the line source approach.

It has been a few years since I fired up my dipoles. Perhaps some people here remember them. Here is the link to the picture

http://www.htguide.com/forum/showthread.php4?t=10095&highlight=Victor

Well, as to the choice of drivers, I still think that what I am using in my system works very well indeed. I particularly like the 10-inch SS 25W58565 array of 4 drivers I am using for the midrange. The woofers are 12-inch Peerless XLS in Linkwitz’s W-boxes. That woofer-mid combination sounds really good. I tried both digital and analog approach to EQ. The digital won me over. I am now fully digital (DCX-DEQ-Roland M-1000), including the volume control! No more op-amps for me!

For music my system is fine, and I like Bach organ recordings. The W-boxes do an honest 20 Hz and are loud enough. However, for the HT applications I would wish for more low frequency extension. So, I am thinking of doing a sealed sub, cross it to the XLSs in W-boxes at around 30 Hz and use for HT only.

Well, as a side note, as I am about to come into possession of two 15-inch Avalanches. Does anyone want to build subs for me, as luck would have it, unfortunately I cannot do any cutting and gluing for a while.

Regards,
Victor

[Dennis H]

The pro drivers being discussed here all have reasonable Qts:
Ciare: .31
Peavey: .34
Eminence: .45

About complex math, you need it if you want to describe both amplitude and phase in a single equation. Life is much easier with PCs and simulation software.

About poles and zeros, my carpenter-level way of getting an intuitive grasp of them is to look at a frequency response graph and not worry about the math behind it. Poles are places where the curve turns downward and zeros are where it turns up. Each pole gives you a 6dB rolloff, down 3dB at Fc. Sum all the poles and zeros together and you get the net curve. If you want a steep crossover, with a sharp shoulder, you are going to need several poles to get the slope and one or more zeros to pull the shoulder up where you want it.

[DIY_newbie]

However, with my limited time to do stuff with speakers, the choice between just doing it (building/testing,etc.) or taking the extra time to document, organize and post coherent info on a website, always seems to slant towards just doing it! Hopefully down the road I will have the time and circumstances to reverse this.
http://www.openbafflespeakers.com

AJ,

I'm heading to look over the site now... If you want some help from another open-baffle nutcase, I'd be glad to help out... Maybe we could incorporate my build project into your website? I've got some extensive computer models for the dipole as well as the theory behind the design...

Now If I could just get the dang things built.. I have the left channel finished, the right is waiting to be glued together in my garage (hopefully tonight).

--Chris

[mikec]

The digital won me over. I am now fully digital (DCX-DEQ-Roland M-1000), including the volume control! No more op-amps for me!

Unless you've done some serious mods to your DCX, there are more opamps in the signal path than you might imagine. :W

[Victor]

[QUOTE=mikec]Unless you've done some serious mods to your DCX, there are more opamps in the signal path than you might imagine. :WQUOTE]

I have complete schematics of the DCX. Its output section has, if memory serves, 4 op-amps in the signal path. The input section is of no concern to me since I am using SPDI/F input. I have only done one modification to the output so far. I replaced one 47 uF electrolytic cap that appears in the signal path with a 10uF polypropylene. The cap is located where the Mute function is. I was thinking about replacing the op-amps also, but in the end I decided to replace the entire output section. I will go with passive L-C-R filter and some discrete transistor buffers.

The original op-amps are not bad at all. I am certain that nobody can really identify them verses any other op-amps in listening tests. I will do the mods only because I can design a better circuit which would result an overall better engineering solution, - and that would make me feel a lot better.

[Davey]

More than likely there were still many op-amps in the signal path before your music was ever mastered onto the CD.

Davey.

[JonMarsh]

Yeah, and some days I think I can hear everyone of them. Fighting a losing battle, I suppose. But that's also why I have quite a number of recordings NOT produced that way - specialty recordings in Jazz and classical. The mixing boards and techniques for a lot of mainstream recordings do leave a lot to be desired.

~Jon