MTM AE TD 10's with XR1464 horn and BMS 4594

Depending where you cross to the BMS, I don't see any problems. I was not a fan of crossing my 4590's that low.

If I could get some XR2064 in Oz, I'd try something similar with JBL 2225 and the 4590s.

I was using my 4590s with Arai radial horns with an Fc at 300Hz. Do a low level FR measurement and they looked good, but they would get very strained in the mids with some level. I never got around to detailed measurements because raising it to 500-600Hz improved it markedly. It stayed there because I had a midbass horn that worked well that high. My hypothesis was that the 4x diaphragm excursion to get the extra octave was taking them out of their linear band.

My concern with an MTM is the C-C spacing of the drivers and how that works out both horizontally and vertically.

"The 400hz xo point seems awfully low on the Noesis's. I would have to think there would be considerable beaming at that point."

what would be beaming? both the horn and the drivers would likely be fairly omni at that point.

the second order distortion on the 4590 goes north around 525hz which is probably what alpha niner was hearing. on the 4594 it is a little lower, around 450hz or so. the 4593 rolls off a little differently, so perhaps that is why the noesis crossover point works. it is kind of like a higher crossover point on the other two drivers.

if you haven't seen pnw's raptor build on htguide, it is a dual 10" mtm with 18sound horn. apparently it worked quite well.

Tsloms, yes, the XT1464 is a better horn. My guess is that JTR used the XR version because it fits his narrower form factor making it useful as a horizontal center channel and the aluminum construction is more durable and dissipates heat for pro use. For home use, if you can do a wider baffle, the XT1464 should be better, but the XR1464 is not bad if that is what you can fit.

I'm not sure I would assume the Noesis has a 400hz crossover point unless that was stated somewhere in detail. The product page says horn loading down to 400hz which is bogus because that horn won't do anything below about 800hz. I haven't seen the BMS coax's used lower than 500hz and that was with very steep filters. I would wait until you get them measured and listened to before assuming what a good crossover point might be. Clearly though 10" woofers should be safe since the Noesis is using 12" woofers at whatever crossover point they actually use.

Here is the only web source I know of: http://www.loudspeakersplus.com/product/XR1464/18-SOUNDXR1464/

Going hybrid active DSP and passive for the coax is a good plan IMO. You really only need to use the passive to filter and get phase in control. The DSP can then EQ the whole bandwidth and filter and time align the woofer to horn.

I say go for it if you know what you are doing on measurements and can model crossovers.

The 8 vs. 16 ohm does not matter much when going active because you can adjust the gain to match levels. If using a passive crossover the 16 ohm would require less padding to match up with the woofers therefore less power is wasted in the resistors.

If you can take some good measurements I suggest trying your hand at crossover design. Like you said I can always look over what you come up with and give pointers where needed.

Based on what I found with the ones that I got when I got my 4590, I'd describe them as crap.

Hello Tsloms, I would question the need for mtm. I don't know a lot about it, but it seems to me that this is used to make the box work better around the crossover point, and create lobing, which will decrease the vertical dispersion, and make it so there is always uniform signal from the mids, in comparison to the highs at the crossover point. This is usually implemented with a dome tweeter. The advantage is that as you move away from one mid, you get closer to the other. Also, it is usually at a frequency where the mids are no longer acting as one unit, so separating them is not as big deal a deal. There are trade offs, but some gains.

In your situation you are at a crossover point where the 12s are still working as one unit, IE, within 1/4 wavelength center to center of the cones. I see this as a big factor. I would mount the 12s one on top of the other for better horizontal coverage, and then do the horn on top of those.

Hello Coctostan, I use the coaxial compression drivers down to 300hz all the time live. I have also used them live crossed over at 300hz on a horn that was no where near big enough to load that low. This was just to see what would happen. I didn't hear them unload, or flap, and there was no damage.


I prefer the 16ohm when I use them active. It is easier to match levels. Also, there are unsubstantiated rumors that the 16 ohm sound better.


My thought is that he will not experience this with the 4594, as much as with the 4590. The 4592, with the neo magnet, has less flux variation throughout the power band. This gives more detailed sound.
Personal preference of course, but I like the mids more from the mid diaphragm than I do from a cone speaker. To me the mid driver has more detail, and better transient response.

Agreed with your MTM/C-C part.

I find the C8-8 and C16-16 quite functional. I have many customers who plan on going active, but get the passives to get started, and then find them so useful that they never go active. Some of the movie houses get one passive, have a tech hook it up, and set up the other channel active, then do a listening test. All of them have ended up going with the passives.

Not sure of your definition of crap is, it is not an esoteric capacitor, but to my mind works great for plug and play.

I did have someone else offer to make me some home rolled crossovers that they had come up with. They had more parts, but did not work as well.
And the guy that I commission to design and build my passives has found no need to improve on their design.

Of course I am all about spending other peoples money, but to my way of thinking, how much time, effort and cost is going to go into just measuring, designing, and building two crossovers?
I have very little experience, and no work flow for this, so it would take me a couple of days.

To me, saving this time, and having it go towards other ends of getting the project off the ground would be worth the money.
And this part of the project could be re-visited at any time down the road. Again the disclaimer that I love to spend other peoples money.

Regards, Jack Arnott
Assistance Audio

PS, for those not involved in the BMS group buy thread, I am the US distributor, and the one selling the product.
Edited by Jack Arnott - 2/24/13 at 11:18pm

Jack, I was just mentioning that in the applications I've seen nobody has used them below 500hz and I believe 96db or 48db slopes were used. I wasn't suggesting that damage would occur just that others have found reasons to not go lower. These were commercial speakers for use in home theaters. I'm not a pro audio guy so I don't know what people are doing for SR usage.

As far as the passive is concerned, if it is fairly cheap it should be tested by tsloms. It would definitely save time. From the response BMS shows on its website it would clearly still need to be EQd so maybe those that found it to be poor we're trying to use it in a full passive speaker assuming it was a more complete crossover. As long as phase is tidy in that range and it is flat in the crossover region it should work fine. I think the phase issue is what people bring up. Sme Internet searching shows that most complaints were with the 2" ferrite version so maybe the problems aren't there for the 4594 passive.

Hello Tsloms, Again, my mtm is a bit rusty, I know enough to be dangerous, but perhaps not all the details. I am more attuned to live sound, and the applications of deployment there. For instance, I use much longer horns, for better pattern control. One of the benefits is that there is less bounce off the walls and ceilings, but I also need to have no spill on the stage, so the mics don't feed back. So having less horn issues with the shorter horns does me no good if the result is the mics are all bouncy, and on the verge of feedback. Also, I know more about coupling as applied to line array technology.

So my experience also leads me back to cinema, and sound systems that are designed for theater. The dual 15", 2" combination is one that goes back decades. And some of the same technology applies. A crossover point of 500hz was established because that is the point where two 15" speakers couple. So that answers that part of the question. If your crossover point is 500hz, you can go up to 15" speakers, and not have to have separate crossovers for each speaker. IIRC, the 12s will go to 600hz. The trade off (everything is trade offs in audio, and we need to try and make the best of the solutions we have) is that it was a but of a stretch for the 2" drivers to go from 500hz, all the way up. So some added tweeters, but the standard pretty much stayed at two way, dual 15"/2".

This is part of my frustration with the 500hz standard. Now that there is a good solution to go lower, there is still the mindset that 500 is optimum. It is a legacy that is tied to the dual 15".

So even in mmt, the dispersion from the cones will compress, get wider and shorter. I don't know how mtm will work with a 500hz crossover point.
I still think the standard developed by cinema stands. Two woofers mounted vertically, and the horn on top of that.
My thought is that mtm is something that is practical with dome tweeters, and high crossover points. But maybe that is my own legacy mindset.

I love the idea of two cabinets, one in each configuration, and comparing them. A/B tests can be subjective, and hard to pull off. And it is hard to not have preconceived notions. But they can also be very powerful, especially if you don't find what you expected to. And I love to hear anecdotal evidence, even if it is empirical.

How will you be crossing over from lows to horns?

Regards, Jack

I guess my ASSumption was that there would be EQ applied from the active crossover, and that it would be applied to the horn as one unit.
So this makes more sense to me now. I think of the BMS passive as mating the two motors together in one unit, and then the overall unit will be modified when it is on a horn, and depending on what horn it is on, the EQing will be different.

If one is to expect the BMS crossover to do all the EQing to make it flat on a horn, it will certainly not do that.

That horn is too small for what you want to accomplish. Even the XT1464 won't make 500Hz with good pattern control. If you do go ahead with it, try a higher XO with "slow" slopes...2nd or 3rd order to get some pattern blend between the woofers and horn.

The woofers and horn would both be onmi at 500hz, at least in the horizontal axis. Vertically the waveguide looses pattern control 2.5 - 3 octaves above the crossover, where as the woofers will be about +-25 degrees at 500hz. I think the shallow slopes is a good idea but not moving the crossover up higher, it is just going to make the directivity transition larger because the waveguide will still be somewhat omni while the pattern from the woofers get even tighter. I think there should be the slow slopes going into the crossover while keeping it rather low but with a shelf filter just below the crossover to protect the CD.

Yeah, at the end of the day it is hearsay. It is best to test the passive and it is probably worth the money to do so. There are certain things that are tougher to fix with active like phase issues though. Using PEQ to smooth to your liking is definitely expected.

Paul, I think this recent craze of going well below where a horn is loading or controlling directivity was started by the positive reviews of the JTR Noesis. It uses this same horn and to the best of my knowledge plays as low as 400-500hz.

What is your take on this approach? I know you use an 800hz cross in your Octagon from horn to mids but I don't think the 18Sound CDs you are using are comfortable playing low like the BMS coaxes.

I'm not sure I would be too concerned about the BMS coax mid. BMS says it can take 1000w RMS above 500hz (no slope indicated). You could probably run these with a 12db cross at 300hz in home use without exceeding xmax. Now what sounds best is not so simple.

I believe they could be made to sound good in a HT application but, personally, I'd try to avoid using small horns too low. Sound good, possibly, directivity control, no. You just can't cheat mother physics!

Yes, with more displacement, the BMS coax should play substantially lower than the ND1460A. The 1460 drivers sound very relaxed crossed ~750-800 and the 32x26" WGs easily achieve my directivity target. My 32" cone/horn center is crossed ~390 but, even trying to cheat with intentional waistbanding, that horn runs short of ideal directivity control....mother physics at work.

Cool, I am digging my Powersoft with built in DSP.
I am familiar with the name Digmoda, but not too much with the product.
I really like Brian from Speakerpower. And his products, although I am not using any right now. One of the few people from the industry that I know.

You are using a 10" woofer, right? Two of those should be great together up to 500hz.

Oh, what part of Italy do you go to for work?

Yes, there is a US vendor. I think they are reasonably priced amps.

Powersoft in Italy don't sell directly to private person, anyhow you should contact the italian distributor that is Showtek http://www.showtek.it/

Ciao

Thats funny, I was on a vacation in Italy for two weeks over the summer with a lot of my family, we agreed Lucca was our favorite town that we had visited. The atmosphere was really nice there, not hectic and crowded with tourists like a lot of the others. You don't work for the toilet paper industry do you?

Sorry this is going to go a little off topic:
After we got back I had built an outdoor projection screen and had it set up for the first time. While testing it out with an InFocus 4805 (not nearly bright enough for the 16' wide screen) I started to hear meowing. At fist I thought it was a neighbor’s cat but then it started to get closer and closer. Finally I saw it right off the patio and grabbed a flashlight to see it better, it ran when I shinned the light on it but it looked small. At this point the wind started to pick up so I took down the screen and brought it to the driveway to roll up. I noticed the cat had now followed me to the driveway and was watching me while still meowing. In the light from the garage I was able to see this was a kitten, only a few weeks old at most. I ended up spending a few hours trying to coax it closer and was able to get it to drink some milk and within a few feet of me but not touching distance. We put a blanket out on the front porch and it slept there overnight. So we decided to adopt it and what name did we give her? We decided to name her after our favorite town in Italy of course, Lucca.