Dipoles like Avro / Orion / Statements, passive XO

[charliemouse]

I’m working on a (WW)wmtmw speaker. I used info gleened from

Jon (https://www.htguide.com/forum/showthread.php?t=7644)
Paul (http://www.geocities.com/pnwright3/Test_Mules.html)
Steve (http://www.doddsy.net/steve6_009.htm)
Jim (https://www.htguide.com/forum/showthread.php?t=25932)
SL (http://www.linkwitzlab.com/builtown.htm)
…and many others here and on the other forum.

Presently I’m using yet another neighbours old wardrobes, and am nearing something I Love the sound of. Thought I’d post for comment before I start looking at exact layout. I’ll follow the pictures with a few details of drivers / crossovers I’m using, and why. I'm still astounded at how fantastic these sound despite being very much experimental. Any pointers as to directions I should take the design in would be very welcome – harsh or otherwise Where am I failing most miserably: layout? Crossover?



Note 1: 10” drivers will be below main panel - like Orion/Avro
Note 2: 45 degree side-baffle suggested by Paul. I’m still working on dimensions
Note 3: MTM distance too large: will decrease in later baffles.


Drivers:
Peerless 10” XXLS 830843
Seas Excel W22 (W22EX001 / E0022)
Visaton TI100
Fountek NeoCD 3 (or Seas 29TAF/W / H1322)

I started a project, building some speakers with Seas Prestige drivers,
- both dipole and boxed
- in TMW vs WMTMW designs.

Dipole or enclosed?
Dipoles built with virtually no design plans way outclassed my Quad 22Ls, and various B&W speakers I have auditioned. I was astounded. Dipole route was chosen without further consideration. Had never heard speakers of that type, but various builds on this group encouraged me to try them.

TMW or WMTMW etc
The project started after discovering that a pair of monitors sat on top of my quads (upside down) gave great presence to many instruments and vocals (clearly comb patterns from high frequencies would be causing problems, but possibly also benefits). I hadn’t previously known about MTM type designs, but reading about Paul’s Mules and various other designs on here, I did some experiments with seas L18 drivers leading me to believe the characteristics of two sets of speakers could be harnessed more constructively in speakers with drivers in a similar pattern.

How many drivers?
Paul’s Mules had four different sized drivers. Jon’s avro designs only 3, but employed construction more like the Orions – and I liked the idea of the lowest frequencies from a U frame: speakers are for music use only and I did not want a sub. Paul’s Mules would probably require a sub of more equalisation than I was looking to use.
Given my L18 drivers shifted far to little air, W22’s had to be used: leaving a hole at low frequencies to be filled by big bass drivers, and a huge gap up to where the tweeter could start.
70s speaker designs, including some old wharfdales I have, often seem exciting and ‘real’ to me. I’m sure they’re inaccurate, I know they lack bass, and they employ pretty poor construction by modern standards. I believe much of what makes them untiring and ‘real’ sound is due to use of a mid between woofer and tweeter; something which has fallen out of fashion, with tweeters having to work down to below 2KHz in various designs. I really wanted a mid, so the hole between W22s and tweeters was very much intended. I hoped dipole woofers would be as tireless on the ears as non-ported 70s boxes too.

Cone types?
I have some Leak speakers: some of the earliest using polystyrene cones and aluminium coating: stiff but light. Very light. A really exciting sound, something the wharfdales (paper/plastic for mid) and certainly the Quads (with a Kevlar cone) don’t have. I chose metal cone drivers throughout.

Drivers
Peerless XXLS – Qts 0.44. These newer drivers were chosen over Linkwitz’s XLS selection as his have such a low Q. I know high Q is bad news, but excessively low Q just needs way too much equalisation: and I want to see if I can get away with passive crossovers. I really thought these were the ones for the job but I’ve never bought a 10” speaker in my life so perhaps a little caution; various people agreed these would be a better choice, so I put down my money and can only thank them for their encouragement.

Seas Excel W22: – super speaker: W26s break up too soon, W18s to weedy. Suitable for dipoles.

Visaton TI100. Much harder to find ‘high mid’ to take me up to ribbons etc. I didn’t want a dome for various reasons. Metal cones aren’t the best choice for taking up high due to break up. I needed small cones because of MTM design, minimising excessive comb interference. Zaph’s TI100 review wasn’t as positive as I’d hoped for, but I bought them anyhow. People love the sound, the break ups at 7KHz and higher look problematic. A few commented the revealing sound may well be a result of the break ups. In line with my thoughts on 70s speakers: what sounds great is not necessarily the straightest frequency response graph. A little taming would probably make them the mid for me. Blow it – I bought them and love the little things.

Fountek NeoCD 3 / Seas 29TAF/W
I don’t know what tweeter I want. Possibly a better dome than the seas with the waveguide, but it does a very good job at its price, and no ugly hexagrid. Metal essential. Listenable, yes, but I want analytical to feature somewhere in the description of the sound.
I’ve never tried ribbons, so am working on using the fountek. You can see one mounted alongside the Seas on one baffle.
I know Millenium will bore me. I need a metal equivalent, but I’m not sure Seas offerings would do it. The problem is there is a jump from £30 to £130 for the top end tweeters. I’m hoping Neos do it, otherwise I’m open to suggestions for a nice top end driver.

Crossovers:
Will post schematics for this shortly:

Passive crossover designer 5.1 for crossovers. Pretty simple so far. Pretty much 2nd order for.

TI100 has slight taming for peak (taken from visaton’s schematics – checked with justMMS, does the trick). Regular bandpass otherwise.

W22 has regular low pass 2nd order, with no capacitor filtering bottom end: I’m using a different amp for XXLSs so only 4ohm min load, not 2!

XXLS – I’m using Jon’s passive crossover for Avro does just what I need. What a coincidence I’ll redraw very badly, (with apologies). Jon’s crossover here: (https://www.htguide.com/forum/showth...&page=15&pp=35) and I didn’t see any point redesigning a wheel designed by an expert... at least until the final speakers are made and I start tweaking

Tweeter – not decided which tweeter to use.

Final note - using passive crossovers as if I move to active, I'll need a lot more cash. it seems pretty daft using a DCX2496, which doesn't even have digital in and out. Years ago I found A 24 bit meridian DAC (certainly a good £1000, can't remember) well outclasses many other DACs. Presumably accurate DA with high slew rates etc provide a superb signal for the pre amps. Re digitising that, post DAC with a Behringer for £100 with cheap op-amps is going to be pretty daft, so unless I buy a load of DACS and processors with digital in and out, passive would seem the way to go. I'm bi-amp, sure, but that's about it. Results so far suggest it is a reasonable route.

Any suggestions?

[Dennis H]

Keep us posted, Charlie! You're way out there on the experimental bleeding edge so all we can do is sit back and enjoy whatever you care to tell us.

[littlesaint]

Final note - using passive crossovers as if I move to active, I'll need a lot more cash. it seems pretty daft using a DCX2496, which doesn't even have digital in and out. Years ago I found A 24 bit meridian DAC (certainly a good £1000, can't remember) well outclasses many other DACs. Presumably accurate DA with high slew rates etc provide a superb signal for the pre amps. Re digitising that, post DAC with a Behringer for £100 with cheap op-amps is going to be pretty daft, so unless I buy a load of DACS and processors with digital in and out, passive would seem the way to go. I'm bi-amp, sure, but that's about it. Results so far suggest it is a reasonable route.

Any suggestions?

The DCX2496 operates with analog signals. It sits between the pre-amp and amp. Analog from Pre to DCX, A->D->processing->D->A, analog from DCX to Amp.

I'm also interested in your results. I'm looking at the same sort of project with the Tang Bangs from Jim's Statements and a waveguide tweeter in an MTM dipole. Dayton woofers in a ported base. Maybe RS270s. A WMTMW is also a possibility. Still working with sims at this point though.

[Tommythecat]

The DCX2496 will accept coaxial spdif into the "C" input (typically rca->xlr). It lists AES/EBU, but the standards are quite similar and I've done it a few times.

[joecarrow]

I think that if I was going to offer some criticism of the overall plan, it would just be to question how low you're running these in dipole mode. Everything I've heard says that dipole has a lot to offer down to 80 hz and below. The Arvo, and Orion both use long excursion 10" or 12" drivers in dipole rather than sealed, and I don't think the designers came to that choice on a whim.

There are some reasons not to go dipole below a couple of hundred hertz, mostly if you're on a tight budget and can't afford enough quantity and quality in the woofers to get the job done. It looks like you're already making a considerable investment, so I just ask- did you think of running it dipole even lower? The W22 is supposed to have best-in-class performance over a range, but I haven't heard anyone call it a bass monster.

[gbyleveldt]

The DCX2496 will accept coaxial spdif into the "C" input (typically rca->xlr). It lists AES/EBU, but the standards are quite similar and I've done it a few times.

Sorry for being off topic guys :B

Tommy, can you point me to a link with the connections for the above? I've tried it but couldn't get it to work.

Cheers

Gert

[Paul W]

Charlie,
One suggestion...there is no mention of a trap for the W22 breakup. The W22 needs a carefully tuned notch, especially if you plan to stay with 2nd order. Minimum 40db down, 50+ better.
Paul

[cadman]

The DCX2496 will accept coaxial spdif

Sorry for being off topic guys :B

Tommy, can you point me to a link with the connections for the above? I've tried it but couldn't get it to work.

Cheers

Gert

take a look at this picture DCX2496

http://www.dcx2496.fr/en/configuration_en.php

[gbyleveldt]

Aaah Thanks!

Thanks Cadman!

I can see now why it did not work.

Gert

[TacoD]

For the tweeter you can also try the ceramic tweeter of Visaton, the KE25 if I'm not mistaken. One of the best measuring tweeters and reasonably priced. Another benefit is that you can get inspiration for the cross-over from existing Visaton designs as this combination is used in their top line DIY designs.

As Paul W is mentioning, the W22 and the TI100 too, need attention in dealing with the resonance peaks.

[ch83575]

I think that if I was going to offer some criticism of the overall plan, it would just be to question how low you're running these in dipole mode. Everything I've heard says that dipole has a lot to offer down to 80 hz and below. The Arvo, and Orion both use long excursion 10" or 12" drivers in dipole rather than sealed, and I don't think the designers came to that choice on a whim.

There are some reasons not to go dipole below a couple of hundred hertz, mostly if you're on a tight budget and can't afford enough quantity and quality in the woofers to get the job done. It looks like you're already making a considerable investment, so I just ask- did you think of running it dipole even lower? The W22 is supposed to have best-in-class performance over a range, but I haven't heard anyone call it a bass monster.

According to John Kreskovsky a dipole's inability to pressurize a room leads to an inevitable and drastic fall-off below the rooms fundamental. Increasing budget may get more clean excursion, but it wont squeeze blood from a turnip.

I do not mean to call into question the full dipole technique in general, I am sure Jon and Siegfried made very informed decisions to use full dipole. I just wanted to point out that budget is probably not the ONLY reason to do a monopole bass section, and that it may very well be specific design considerations that influence the decision as well.

[Davey]

Sorry for being off topic again. Input A, not Input C is the AES/EBU digital input on the DCX2496. The unit will toggle a relay internally to route the connector to a different destination. This can be selected either with the front panel controls or....more easily...with the DCX2496 Windows GUI.

Interesting dipole project. 'Looks like a lot of work to me.

Cheers,

Davey.

[JonP]

According to John Kreskovsky a dipole's inability to pressurize a room leads to an inevitable and drastic fall-off below the rooms fundamental. Increasing budget may get more clean excursion, but it wont squeeze blood from a turnip.

I do not mean to call into question the full dipole technique in general, I am sure Jon and Siegfried made very informed decisions to use full dipole. I just wanted to point out that budget is probably not the ONLY reason to do a monopole bass section, and that it may very well be specific design considerations that influence the decision as well.

Also note, that SL has an optional monopole subwoofer that is intended to be crossed very low... I imagine that the reason would be for exactly that reason, to fill in the lowest octave where the dipole dual 12's roll off?

[charliemouse]

Lots of posts, great. On the secondary discussion, I think I'll have to get a DCX 2496, and see how much damage it does to the signal... I'm still concerned that nice beefy power supplied DAC and pre amp will have their benefits debased quite spectacularly by cheap op-amps in behringer, but I should at least give it a go.

On the project in hand - a question on filtering:
One reason for experimenting away rather than designing it all first, is I wanted to listen to how changes in crossovers effected the sound (rather than look at graphs).


The TI100 is clearly the most troublesome. With 2nd order bandpass at 800Hz and 4KHz, and no filtering for breakup (Some crude measurements at 1.5m away - so wobbly due to room interference etc.):



8O

With 0.22Mh 2.2uF 4ohm series filter (parallel to driver, lower resistance takes peak of more obviously)





Using 4th order filter, something like a reasonable cut off is measured:





But... Which would you imagine sounds the better?

It might be a bit bright, but despite the fact the drivers are working well over the tweeter's range, the gentle notch filter sounds much better than the 4th order crossover. The 4th order crossover looses so much life from voices etc.

I'm not entirely sure where I'm going with this: I should imagine stronger filters for the 7KHzbreakup, and another deep one for higher breakups.

What is quite apparent is comments elsewhere about the breakup of these drivers being responsible for their clear sound are something I'd certainly now agree with. If I filter so much I get a flat response, they will loose their edge. Fortunately these speakers are for me, not for a sales catalogue: so suspicious looking frequency responses aren't an 'end-all'. At the same time, I clearly need to do some work on these.

W22 presenting little problems so far: certainly less of a ridiculous breakup than the TI100s.

[charliemouse]

According to John Kreskovsky a dipole's inability to pressurize a room leads to an inevitable and drastic fall-off below the rooms fundamental. Increasing budget may get more clean excursion, but it wont squeeze blood from a turnip.

I do not mean to call into question the full dipole technique in general, I am sure Jon and Siegfried made very informed decisions to use full dipole. I just wanted to point out that budget is probably not the ONLY reason to do a monopole bass section, and that it may very well be specific design considerations that influence the decision as well.

Also note, that SL has an optional monopole subwoofer that is intended to be crossed very low... I imagine that the reason would be for exactly that reason, to fill in the lowest octave where the dipole dual 12's roll off?

This is Jon Marsh's crossover for driver D1 (I've linked to his upload here), his thread is here https://www.htguide.com/forum/showth...&page=15&pp=35


nb - only referring to top crossover, and reiterate - this is Jon's work!

Using this and the lovely drivers I mentioned earlier in a not-lovely-chipboard-box-with-inadequate-bracing-etc I have the best bass I've heard in my living room.

I did a few experiments before investing, but my thoughts went along these lines. Do tear them apart if there are any experts. As long as my ears are happy, I'm not bothered the the theory is rubbish!

So: You can have a large set of floor standers, with superb bass extension. Sound great in dem room. Take them home to 6x7meter room, or perhaps a 4x5, or a 5x9 (being some I've tried), with bay windows, various ceiling heights etc... and the disappointment is guaranteed every time.

I imagine standing waves are problematic in particular. The bass from these speakers is spectacular upstairs :roll:

I'm still taking measurements of these u-frame boxes I'm working on, but using my fourier transform analyzers strapped to the side of my skull and wired direcly into my auditory cortex I can report the bass is stunning. Whatever measurements I get, I know the sound of an upright bass and a drum kit very well (I'm a musician, as well as a computer/electronics geek - it gets worse doesn't it) and the sound these things produce is inordinately closer to the real thing than any sealed box I've heard. Bottom E on a bass is 42.1Hz. These produce a very natural sounding 42.1Hz it seems, and whilst 21.05Hz etc will exist, working on perfecting these but loosing the dipole bass would be a real step back for me. It may be essential for explosions on movies, but the last movie I watched was by an obscure comedian from Sheffield so my taste quality films as well as my enthusiasm for subsonic response are low. I'm waffling.

Anyhow. Any thoughts on the ridiculous response of that beautiful-sounding, vile-recording TI100 are particularly sought after.

Robin (erm, Charliemouse is a character in an old UK children's TV program. I'm neither called charlie nor rodent)

[Dennis H]

Also note, that SL has an optional monopole subwoofer that is intended to be crossed very low... I imagine that the reason would be for exactly that reason, to fill in the lowest octave where the dipole dual 12's roll off?

Yeah, last I heard, he's using his monopole subs all the time now, crossed to the Orions at 50Hz. Which kinda makes you go hmmmm.... Half the cost of the Orion (for each speaker: 2 drivers, 2 amps, the hardest part of the cabinet) is only covering a bit over an octave, from 50 to 120. Of course the Orion was designed to play all the way down to 20 and the subs were an afterthought. Seems to me, if you're starting from scratch and you know you're going monopole down low, the dipole bass section could be designed to cover a bit more bandwidth, say at least 2 octaves.

[Paul W]

Running pink noise through the system (and single drivers) can help highlight resonances that may grow tiring over the coming weeks. Issues that might otherwise go unnoticed for a while (or, worse, never identified) stand out very quickly with pink noise. Listen off-axis vertically as well as horizontally, and at different distances. A trap or two on the W22 and TI100 will likely help achieve a more natural soundscape...like walking near a waterfall.

No idea what the woofer response is but, just based on visual depth of the U, be on the lookout for an acoustic peak around 200-300Hz.

[JonMarsh]

Yeah, last I heard, he's using his monopole subs all the time now, crossed to the Orions at 50Hz. Which kinda makes you go hmmmm.... Half the cost of the Orion (for each speaker: 2 drivers, 2 amps, the hardest part of the cabinet) is only covering a bit over an octave, from 50 to 120. Of course the Orion was designed to play all the way down to 20 and the subs were an afterthought. Seems to me, if you're starting from scratch and you know you're going monopole down low, the dipole bass section could be designed to cover a bit more bandwidth, say at least 2 octaves.

Yeah, but not in an H frame.... or U. IMO. YMMV. All the usual disclaimers of responsibility; i.e., it's just my opinion. :W

Trouble also is getting "subwoofers" to work up higher. The trick, I'm afraid is finding a driver that can go up higher, and make life easier for the midrange. But it will have to have a special motor, something like the RS sub drivers, or the Aurasound. Lots of copper in the gap to keep the inductivity modulation down with increasing excursion.

OTOH, having true dipole bass, upper bass, etc, from 50 Hz or so up is a big deal, IMO. One might even use 75 Hz as a cut off point, but you're getting into a range there where the room issues for monopoles come on strong...


VERY good comment from Paul, IMO; Pink noise shows up all sorts of nasty stuff in power response and resonance- if you can get pink noise sounding smooth over a wide range of the listening area, you're doing more than a few things right.

Back in the 70's it used to be that the only things I used for testing (besides a good LCR meter) was 1 msec square wave pules and pink noise- none of the new fangled MLS testing was available for average joe's like me. If you could get a good clean flat top 1 msec pulse, and decently smooth pink noise (great for initial driver selection, too!), you were probably in the ball park. Wish I still had some photo's of some of those scope waveforms.

[Dennis H]

Yeah, but not in an H frame.... or U. IMO. YMMV. All the usual disclaimers of responsibility; i.e., it's just my opinion.

Ditto that. Pro driver(s) and a flat or very shallow U baffle. Hmmmm, Isiris anyone?

[AJINFLA]

I've got a pair of Peavey Lo rider 18's sitting around for months now that I really need to finish the baffles for. Now Jon's looking at Aura 1808's :E . Oh my.

cheers,

AJ

[Beau]

Hmm, Im in the same boat. Ive got a pair of Eminence 18LF drivers sitting around here along with my recently aquired C173n-t6-90's (Damn they are heavy!!!) The thought of buying those Auras I just cant quite justify.. Have you seen Acoustic Elegance is back online? They have got some potential drivers, The IB15 woofers for example.

Beau

[charliemouse]

Running pink noise through the system (and single drivers) can help highlight resonances that may grow tiring over the coming weeks. Issues that might otherwise go unnoticed for a while (or, worse, never identified) stand out very quickly with pink noise. Listen off-axis vertically as well as horizontally, and at different distances. A trap or two on the W22 and TI100 will likely help achieve a more natural soundscape...like walking near a waterfall.

VERY good comment from Paul, IMO; Pink noise shows up all sorts of nasty stuff in power response and resonance- if you can get pink noise sounding smooth over a wide range of the listening area, you're doing more than a few things right.

Thanks guys. I like that idea. Sounds like a nice halfway house between MMS measurements and listening through various musical pieces. The former two tools would clearly each point to a certain crossover configuration, but pink noise is, I guess, going to give me a further point of reference.
I picked up bag of extra capacitors and resitors etc on the way home from work on Friday, so fingers crossed I've a sensible comprimise between killing the breakups dead whilst dulling the music, and letting them add so much they introduce too much that was not present in the source to be acceptable.

OTOH, having true dipole bass, upper bass, etc, from 50 Hz or so up is a big deal, IMO. One might even use 75 Hz as a cut off point, but you're getting into a range there where the room issues for monopoles come on strong...

Indeed. Commenting from nothing more than my biased perception: anything I'm loosing below 50Hz, is presently more than made up for by the superbly natural reproduction above that with the dipoles. I know on paper, for example, my Quad 22Ls drop off less than these dipoles in their temporary housing - but to the ear, the bass is in some parts boomy, and in others non-existent. Taking them to a dem room to compare to others, I'm always surprised that they are my speakers playing - dipole makes the quantum leap in hi-fi reproduction at home that nothing else I auditioned could do.

As I probably said before - the information the web and particularly this forum has been the foundation for experiments thus far. I'm particularly grateful as whilst there is an outlay in terms of drivers & time, it was a huge upgrade in knowledge not financial outlay that helped.

Back to playing, and a little time trying to work out where I can source some huge pieces of real wood rather than having to laminate. Large teak lab benches are a keen favourite to be thrown out these days, better make some enquiries...

[ThomasW]

Hmm, Im in the same boat. Ive got a pair of Eminence 18LF drivers sitting around here along with my recently aquired C173n-t6-90's (Damn they are heavy!!!) The thought of buying those Auras I just cant quite justify.. Have you seen Acoustic Elegance is back online? They have got some potential drivers, The IB15 woofers for example.

Beau

Grab a pair of the BMS 4540ND compression tweeters with the DDS ENG 1-90 wave guide. Then you'll have the parts needed to build a version of the Isiris ... :T

There will be several woofer/midwoofer versions of the Isiris/Isiris Jr.

Current plan for builders with different woofers is for Jon to design a passive XO for the MT section. People will use a generic active XO for the woofers. EQ will be handled by an outboard box (even the lowly BFD should work)

[Beau]

Thanks Thomas, they are already on their way. I was hoping that would be the case as I already have a cx2310 so things should work out nicely.
(Sorry to hijack the thread)

[JonP]

VERY good comment from Paul, IMO; Pink noise shows up all sorts of nasty stuff in power response and resonance- if you can get pink noise sounding smooth over a wide range of the listening area, you're doing more than a few things right.

Back in the 70's it used to be that the only things I used for testing (besides a good LCR meter) was 1 msec square wave pules and pink noise- none of the new fangled MLS testing was available for average joe's like me. If you could get a good clean flat top 1 msec pulse, and decently smooth pink noise (great for initial driver selection, too!), you were probably in the ball park. Wish I still had some photo's of some of those scope waveforms.

Wondering if you or others have used that "Sound Strobe" tester written up a couple of times in AudioXpress? I think one can still get it as a kit, or bare board... besides as an assembled device. For those who don't know, it produces various exponential pulses, pink noise, etc for speaker and system testing. I've thought of getting the bare board and stuffing one up...

Sound Strobe info

[Jonasz]

Grab a pair of the BMS 4540ND compression tweeters with the DDS ENG 1-90 wave guide

Thomas, how low could that tweeter/waveguide combo be used?

[ThomasW]

Thomas, how low could that tweeter/waveguide combo be used?

Checkout the Isiris thread for recommendations...

https://www.htguide.com/forum/showthread.php?t=23598

[charliemouse]

No idea what the woofer response is but, just based on visual depth of the U, be on the lookout for an acoustic peak around 200-300Hz.

Using crossover listed, cross is at 200Hz - and there is indeed a bit of a peak around there.

How did you know?! OK, can work out resonant frequencies for boxes with various bits of software, and all the necessary driver TS parameters etc... but what governs the peak of a U?! It is indeed a box, but quite how the minimal difference of 'one missing side' alters formulea I've no idea?! A port with the area of a side?!

Active vs Passive
I'm having problems actually: For example I would have liked to try some subtle changes to crossover for XXLS drivers. Components are so damn expensive, and I'm being cheap and using ferrite cores (decent quality low resistance, but nonetheless...). I used expensive electrolytics for sub crossover but I also found a discrepency between mid response on which I used 'any old audio grade caps'. This confused me for days but resulted from a 6uF poly on one side and a 4uF poly on the other with a 2uF bipolar electrolytic in parallel to get 6uF. Both channels caps measure 6 +/-0.05uF. Electronics technician at work suggested the cheap electrolytic may well be seen as a lower value to the high frequencies :roll:

I'm thinking on possibility of playing with active (I've 3 matched power amps so that isn't a hurdle) - only I'm still not happy with DCX2496. Other comments on this and other boards suggest it is adequate but not superb. As mentioned before, if a veyr expensive meridian DAC can clearly improve sound before pre amp, samplying the lot again after the pre amp with the Behringer can't fail but cause problems.

I am considering using passives in active cross over using opamps. Building myself would allow trying different crossover slopes and compensation circuits, but when i last built an amp (15 years ago) I spent years pratting around with it, so I'm still undecided.

[Dennis H]

but what governs the peak of a U?!

In theory, it's a transmission line so the resonance is where the U depth is 1/4 wavelength but, as SL points out, the basket and other factors can change that quite a bit. He recommends measuring it with the mic at the rear exit.

[AJINFLA]

Hi Charles,

Perhaps you could arrange for a visit with this gentleman to hear his DCX system and see if it reconciles with what you have read on the internet? That system should be capable of revealing any bottleneck created by the DCX, real or imagined IMHO. Have you also considered a hybrid passive/active approach, with the DSP processor operating below the mid/tweeters only?

cheers,

AJ

[Paul W]

How did you know?!

It's black magic!!! (Actually, I just eyeballed 1/4 wave.)

JohnK's site will also give you great insight into U baffles. John uses fiberglass stuffing to damp the resonance, another approach is electronic EQ, my preferred solution is a semi-cylinder of (real) wool felt curved from front corner to front corner and as deep as possible without opening the top and bottom of the U (keep the felt away from the driver). Felt anywhere from about 6-12mm thick, depending on felt density, driver, and U.

I believe the DCX2496 is very underrated. Of course you can do better, but I think it is a darned fine box for you at this stage, especially if you are using ferrite cores and electrolytics to save cost. You can tweak to your hearts content then, to squeeze the last bit of performance, translate the DCX transfer functions into a passive crossover with high-end components. Like AJ suggests, hybrid is also a great way to go...I've done it many times and it works very well.

[charliemouse]

Thanks very much all three of you... ;x(
I've progressed much faster since resolving the capacitor problems. I'm probably making my corssover materials sound worse than they are. I'm not sure if using ferrite cores on the 1mH+ inductors shapes the signals too horribly - lower values are air core anyhow. I'm fairly pleased with visaton electrolytics for the high values e.g. 200uF (using decent caps for 30uF downwards). I would certainly want to have a good crossover using them before I invested in lots of film caps.

... I think I should consider buying a unit to give it a go - it is clear you are all experts from your posts and designs, so I ought to take your advice on the unit if I go active. One other expense first -

Tweeters - which one?
I should probably ask this in another thread. I've compared Seas 29TAF/W with Fountek NeoCD3 and prefer both :roll:

The seas is I assume like the good value 27mm metal tweeters, though I don't have one to compare. Airiness of hi hat etc on the fountek is superior to seas, but tonality in plectrum clicks on acoustic guitar and a number of other tonal issues are suerpior on the seas.

I don't know whether directionality of the ribbon in MTM is problematic (not in statements it seems).

Question therefore: if I'm happy to spend $170ish per driver - are there any metal domes that might produce highs cleanly and analytically, but have superior tonality to the ribbons. Seas Excel T29AF001 , scanspeak 980000 , and Hiquphon OW4 (expensive? Haven't enquired with them yet, and would like to see other builds first).

I'm not sure if this thread is the right place to ask as it might not help people looking in the future - let me know and I'll post in a separate thread if you suggest.

Thanks

[Paul W]

No direct experience with any of the tweeters you mention, so this is just FWIW...

I used the OW1 in the Mules and eventually decided 19mm domes were not a good MTM match. Relative to the restricted vertical dispersion of a mid pair, the broad dispersion of a small dome results in a vertical "flare" above crossover. This vertical flare led to a large ribbon in the next generation...and that ribbon worked extremely well. However, no idea how low the Fountek will play before distortion creeps up, but that may be the challenge with it.

[charliemouse]

No direct experience with any of the tweeters you mention, so this is just FWIW...

I used the OW1 in the Mules and eventually decided 19mm domes were not a good MTM match. Relative to the restricted vertical dispersion of a mid pair, the broad dispersion of a small dome results in a vertical "flare" above crossover. This vertical flare led to a large ribbon in the next generation...and that ribbon worked extremely well. However, no idea how low the Fountek will play before distortion creeps up, but that may be the challenge with it.

Ah - perhaps the restricted vertical dispersion of the Fountek is good then? It certainly has the edge at the higher frequencies (shimmer of cymbals etc) - but tonality less. Perhaps I need to play with crossover frequencies. This crossover is the most challenging: taming TI100breakup, limiting frequency by mid-mid pole distance, a real problem getting phase to match, 5K-7K displaying temporary flattening of phase line etc (still not sure why!)

Quick check of my notes on your design, Paul, (I wonder if keeping detailed files on drivers / designs / frequencies of others' designs is getting a bit excessive ) suggests 3.2KHz on yours - I should probably lower mine a little, see if that helps. I didn't imagine the ribbon would have much body in the low 3000s though.
It is quite quite possible it is not the tweeter that is at fault, but the crossover. Having said that, BMM just gave me another 10% voucher for a coil they didn't send - so I'd risk one more tweeter driver purchase at my next buy! Other's suggestions still welcome (though the chance you're reading this far down a thread on a design is unlikely)

[Dennis H]

You might try a B&G Neo3PDR with the back cup removed if you want to experiment with dipole treble. It measured better than the pure ribbons in Zaph's test. Zaph thought it was overdamped with the rear chamber removed but he was using it in a monopole enclosure. In a dipole you get a baffle boost down low.

http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=264-735

http://www.zaphaudio.com/nondomes/

[charliemouse]

Thanks for idea Dennis.

Having a bit more joy with NeoCD3 this evening - partly in relation to TI100 for which I'm finding 2nd order together with parallel filters for breakups is probably better than higher orders: I presume because the more that is in series, the less the amp can control resonance through back EMF.

Ooooh, I found a little mentioned DCX2496 equivalent - which one review considered much better.

http://www.bmm-electronics.com/Product.asp?Product_ID=4893

I'm still not convinced a whole set of DACS at that price can replace the meridian 566 DAC. I know technology moves on, but the last one sold on ebay went for over £500. Then again - I started this thread mentioning some wardrobe doors with a grands worth of drivers attached sounds uncomparably superior to a carefully designed Quad speaker at a similar cost. Too many questions floating around the head. I'll go to bed. :Z

[Jed]

Too many questions floating around the head. I'll go to bed. :Z

Haven't you noticed, nobody sleeps around here? Seriously, I like your speakers so far. I really need to try a dipole next.

[Jonasz]

Just some random thoughts...

You could sell the Visatons and buy TB and build the Statement MTM-part with the Fountek. (It's a dipole mid, sort of...) http://www.geocities.com/cc00541/Statements.html

Neo3PDR sounds pretty darn good! :T

Seas will have a waveguidetweeter with aludome for sale late this year or just after the new year. It would fit a dipole radiationpattern better than most other tweeters. I think anyway...

As I said, just some random thoughts...I'm more or less in the same dilemma myself...

[chasw98]

Charlie:
I am in the midst of a project similar, sort of, to yours. I have built a basic set of Arvo dipoles with a DCX2496 acting as the preamp so to speak.



The source goes directly to a DEQ2496 using an AES/EBU matching transformer, then to the DCX2496, and on to my DIY custom remote control 6 channel passive volume control. AFter that it goes to the amps. I am going 2 way with a sub right now while I sort out the last little electronic and hardware details. Then I can start listening and measuring. I think I will eventually try some sort of waveguide to see how that goes. So far the DEQ & DCX seem to be very good pieces of gear as far as fidelity goes. I should have the system going through trials this weekend and then be able to comment with a bit more authority about it. Right now it is like having a pair of gravestones in the living room with a lot of wires on the floor.

Chuck

[JonMarsh]

Right now it is like having a pair of gravestones in the living room with a lot of wires on the floor.

Chuck

Wow, what a visual image!

~Jon

[Kevin Haskins]

The Neo3PDR gets my vote. I just built one yesterday and its a fairly simple solution to work with. Its handles a low crossover point with ease, has a true dipole dispersion with the rear cup removed, and for $50 its hard to get that type of performance.

Its only difficulty was the need for a notch filter up around 12K on my baffle with the rear cup removed. Other than that it was an easy solution at 1.8K 4th order acoustic.

[augerpro]

How is the horizontal dispersion of the Neo3PDR and ribbons compared to a typical dome?

[Kevin Haskins]

How is the horizontal dispersion of the Neo3PDR and ribbons compared to a typical dome?

I've not done a lot of A/B/C/D comparisons on the same set of measurements. From the seat of the pants... I'd say its close to a typical 1" dome in terms of horizontal off-axis.

I don't like ribbons so I've not done a lot of measurements with them. In general though... the narrower the ribbon, the wider the dispersion pattern. Of course the narrower the ribbon the less the power handling and they all make good Christmas tree tinsel after just one test tone if you don't put a cap on them.

[charliemouse]

You could sell the Visatons and buy TB and build the Statement MTM-part with the Fountek. (It's a dipole mid, sort of...) http://www.geocities.com/cc00541/Statements.html

Neo3PDR sounds pretty darn good! :T

Seas will have a waveguidetweeter with aludome for sale late this year or just after the new year. It would fit a dipole radiationpattern better than most other tweeters. I think anyway...

As I said, just some random thoughts...I'm more or less in the same dilemma myself...

Quite. These were the two chooses for mids for a while - but the tangbands were half the value of the visatons in Europe. I'm really happy with the sound, despite the effort the breakups need.

The seas tweeter I have is alu dome with a waveguide - see picture earlier. Are they bringing out another one? If it doesn't have such a drop off up from 15K that would be good news. I wonder if the 15k drop off is the problem? I can hear 15/16K - higher doesn't work now I'm in my 30s. At the same time I know high frequencies combined produce low frequencies, hmm. Further ponderings.

I've not done a lot of A/B/C/D comparisons on the same set of measurements. From the seat of the pants... I'd say its close to a typical 1" dome in terms of horizontal off-axis.

I don't like ribbons so I've not done a lot of measurements with them. In general though... the narrower the ribbon, the wider the dispersion pattern. Of course the narrower the ribbon the less the power handling and they all make good Christmas tree tinsel after just one test tone if you don't put a cap on them.

Interesting - you mentioned using them, but also not liking them. Is that following from using them? I'd interested to know what you don't like. I have certain issues with them, but it could be more related to what they're paired with.

re dispersion 20 degrees down on vertical and there is a huge audible change in response. I've not spend ages measuring either. If you take one, no baffle, and tip it just away from you (vetically, not horizontally) - compare pink noise / mms signals, and it is as if all the very high frequencies aren't even there. Quite astounding. Horizonatl dispersion simlar to dome, yes (well, by ear).

Haven't you noticed, nobody sleeps around here? Seriously, I like your speakers so far. I really need to try a dipole next.

Do they all put their backs out too? I think many hours of twisting changing resitor values on tweeter, whilst listening and scrabbling around for bits on the floor did my back some mischief. The muscles were so upset I couldn't get much air into my lungs if I tried lying down and had to wander around the house until 4 in the morning when I could bear to lie down. Getting much better and decided some longer leads and a bence with crossovers in front of a chair (not on the floor) would be a sensible project before I continue experiments.

Charlie:
I am in the midst of a project similar, sort of, to yours. I have built a basic set of Arvo dipoles with a DCX2496 acting as the preamp so to speak.

...
...

I should have the system going through trials this weekend and then be able to comment with a bit more authority about it. Right now it is like having a pair of gravestones in the living room with a lot of wires on the floor.

Chuck

Let us/me know how it goes. It is exciting so many people have similar projects.

Jean from BMM electronics is knowledgable on many speaker issues (they sell audio components), but suggested some caution re that sort of level of crossover in hifi rather than PA use. I think I'll get :T and :nono: in varying amounts from everyone I ask.

[charliemouse]

Metal domed tweeters - what else should I consider (ideally seas / scanspeak / any from BMM i.e. easily available in europe).

I know dispersion ought to be addressed with waveguide... but I'm interested to try one more dome before I use my fountek. There's something harsh about the projection from the ribbons - I'm still happier (listening, not necessarily on paper with response) with integration of the seas dome I have.

Thanks