SEOS-24™ brutal dual 18" three-way LCR build - AVS Forum
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post #1 of 92 Old 01-30-2014, 04:02 PM - Thread Starter
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Thanks to the help and suggestions from several guys here, all the drivers are selected so it is the moment to start a build thread. Over the years, I have been all over the place deciding this!

For a semi-dedicated homecinema in a new house build, I want to build all the speakers starting with the center and then the left and right front speakers. Each LCR uses the same drivers, but since the center is put behind the 330 x 140 cm (130 x 55") 2.35/1 acoustic transparent XD screen from Seymour, which is visually floating, the box shape will be different. It is easier to make, so I want to have a go at that one before making the towers.

The room is about 22.8 x 28.4 x 8.7 feet hence more than 5,000 cubic feet. It is a box-in-box construction on top of a floating concrete floor to keep the noise sound inside. I checked the room ratio at Salford University website and it rates among the "best". Not my merit, just pure luck. I have also been consulting an acoustician to implement room treatments. I fancy diffusion elements which will be used behind the AT screen (flanking the center speaker), on the side walls, the back wall and the ceiling. Then a reverberation measurement will be executed which will enable us to decide on extra absorption, most likely in the bass region.

Two subs are long ready using 18" Maelströms. 550 liters each, "LLT" tuned to 13 Hz. I might add two more (sonotubes) if necessary.

The parts:
  • SEOS-24™ waveguide
  • BMS 4594ND coaxial 1.4"
  • EighteenSound 15ND930 [2] / or Beyma 18P80Nd [2]

The idea is to use a passive x-over between the BMS tweeter and mid (@6,300 Hz) and use a miniDSP 10x10 HD as an active x-over between the bass and mid @ 450 Hz since that is where ChopShop has it. The 15ND930 was suggested to me because it is suitable for a lower tune than most pro 15 inches. It is still 98 dB / Watt sensitive which theoretically gets me 125 dB @ 1 meter using the Emotiva XPR-5 (600 Watt @ 4 ohm). That should be enough for our 12 feet listening distance... Acoustic Energy, although specced great, was not a viable option since these do not seem to be represented in EU. Woofers are expensive to ship! The 15ND930 can be had for less than €250 including delivery.

The recommended enclosure volume is 60 - 140 liters (2.12 - 4.95 cu-ft). I made the exercise and I can actually stretch to 140 liter net volume for each woofer (320 liter gross internal with braces before the volume of the drivers and ports are counted for).

Now I have to figure out which tune and what size the ports have to be. Is there Mac-usable software out there? Or is there a good soul who could do the math for me? i would like to try to set the x-over to the subs as low as 45 Hz, the threshold of directivity. Maybe I end up higher, but it would be cool to have the option.

The two L+R towers would be MTM which puts the SEOS-24™ centered @ 1 m height (yes, you guessed it, they are 2 m height). This leaves two options for the center:
  1. MTM layout which puts the SEOS-24™ @ 1.25 m height. I guess I can tilt it downwards a bit to aim at MLP.
  2. MMT layout with both woofers on top, which puts the SEOS-24™ @ the same height as the L+R. Is that good practice? If the woofers would have been crossed higher, then I guess not, but I presume I am okay up to 450 Hz? This would be my preferred option.

I would use 30 mm MDF and apply more than enough bracing.

Any suggestions very much appreciated.

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post #2 of 92 Old 01-30-2014, 04:07 PM - Thread Starter
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The subs:
P2161237.jpg 35k .jpg file
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post #3 of 92 Old 01-30-2014, 04:15 PM
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I'm surprised Jake's ears aren't burning yet. smile.gif

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post #4 of 92 Old 01-30-2014, 04:22 PM
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Ironically, I have 6 of the eighteen sound 15ND930 since having the Yorkville u215s and 3 seos 24s just missing the bms compression drivers if I ever decided to tinker.
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post #5 of 92 Old 01-31-2014, 12:16 AM
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How does the 18sound XT1464 compare to the SEOS-24 waveguides?
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post #6 of 92 Old 01-31-2014, 06:36 AM
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Quote:
Originally Posted by jbrown15 View Post

How does the 18sound XT1464 compare to the SEOS-24 waveguides?

I think the Seos-24 will hold patern down lower than the XT1464, allowing for a lower crossover point between the compression driver and woofer. The Seos-24 is a lot bigger, physically, as well.
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post #7 of 92 Old 01-31-2014, 09:23 AM
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Some comments/questions,

So I didn't really follow the other super big SEOS builds but is there any measurements and distortion measurements of the BMS on the SEOS24? I am really surprised by the 450hz xo point. Given that a SEOS WG doesn't really provide much loading, unlike a horn, I would think the distortion would be through the roof below say 600-700hz. I would have guessed (without data) that this would be the ideal xo point. Again, I haven't see the data but given what I know about the waveguide design, that would be what I thought.

Second, are you considering doing a 2.5 way setup? The center to center distance using a massive waveguide and 15" woofers in MTM means a huge amount of combing and small forward lobe. Given your seating position is 12' away, I'd think a 2.5 way config might be more ideal. Since you are using a miniDSP 10x10 you have plenty of channels available to make that much easier.

It would just suck to expect way better results by building bigger and better and actually get worse results because of poor execution, which is why I ask the question.

I think the MMT upside down would be just fine if you properly orient the front lobe and do it 2.5 way again.

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post #8 of 92 Old 01-31-2014, 09:46 AM
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Distortion of the 4594 on the SEOS-24 starts to rise below 500hz or so, a 450hz crossover keeps it well tamed.

I was just playing around with the driver for this measurement, I don't know what distance I used or if the levels were calibrated but it gives you an idea of what the distortion does in the SEOS-24.
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post #9 of 92 Old 01-31-2014, 09:47 AM
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Quote:
Originally Posted by Martycool007 View Post

I think the Seos-24 will hold patern down lower than the XT1464, allowing for a lower crossover point between the compression driver and woofer. The Seos-24 is a lot bigger, physically, as well.

How the heck does Jeff from JTR get away with using the even smaller XR1464 and crossing over the BMS 4593 so low in his 212HT's confused.gif
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post #10 of 92 Old 01-31-2014, 09:48 AM - Thread Starter
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ChopShop's build with the same horn and coaxial:

http://www.avsforum.com/t/1457166/s-e-o-s-r-mega-build/1350#post_24251859

Isn't the combing frequency dependent? The center to center distance of the dual 15" will be like 80 cm (31,5") but they will only be used up to 450 Hz.

I can also swap the dual 15" for one 18".

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post #11 of 92 Old 01-31-2014, 09:53 AM - Thread Starter
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Quote:
Originally Posted by Martycool007 View Post

I think the Seos-24 will hold patern down lower than the XT1464, allowing for a lower crossover point between the compression driver and woofer. The Seos-24 is a lot bigger, physically, as well.

That and the XT1464 is designed as a 60° horizontal dispersion where the SEOS-24™ is 90° if I remember correctly. I suppose the XT1464 is aimed at higher SPL also. The only real downside is that the SEOS-24™ is bloody wide!

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post #12 of 92 Old 01-31-2014, 09:55 AM
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Quote:
Originally Posted by jbrown15 View Post

How the heck does Jeff from JTR get away with using the even smaller XR1464 and crossing over the BMS 4593 so low in his 212HT's confused.gif

Because at the lower crossover both woofer and horn are mostly omnidirectional therefore dispersion patterns still match up.
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post #13 of 92 Old 01-31-2014, 09:58 AM - Thread Starter
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Quote:
Originally Posted by jbrown15 View Post

How the heck does Jeff from JTR get away with using the even smaller XR1464 and crossing over the BMS 4593 so low in his 212HT's confused.gif

And to know that the recommended min x-over is 800 Hz...
http://www.eighteensound.com/index.aspx?mainMenu=view_product_simple&pid=268

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post #14 of 92 Old 01-31-2014, 09:59 AM
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Here's my distortion measurement of the SEOS-24(1.4" entrance) at 1m.


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post #15 of 92 Old 01-31-2014, 10:22 AM - Thread Starter
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Quote:
Originally Posted by AudioJosh View Post


Second, are you considering doing a 2.5 way setup? The center to center distance using a massive waveguide and 15" woofers in MTM means a huge amount of combing and small forward lobe. Given your seating position is 12' away, I'd think a 2.5 way config might be more ideal.
You are aware that the BMS4594ND coaxial is already a 2 way, right? So if I divide the dual 15" again that would make it a 3,5 way, not?

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post #16 of 92 Old 01-31-2014, 11:13 AM
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I'd say that looks ok at 500hz xo, given those measurements, *I* personally wouldn't go lower than 500hz, probably 550 to be safe. Yeah, sorry forgot about the coax driver, I was merely commenting on the .5.

Yes, combing is freq dependent, but a 450hz wave is ~24" long, so waveguide's to outer woofer space will still cause combing at 450hz. Its one of the reasons why when we designed the SEOS we made the vertical shorter than the horizontal to widen the vertical lobe between the waveguide and the woofer. When you add the second woofer the distance is a whole driver diameter further away.

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post #17 of 92 Old 01-31-2014, 12:53 PM
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Oh this looks like a delicious large speaker build. Love it!
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post #18 of 92 Old 01-31-2014, 04:23 PM - Thread Starter
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Oh this looks like a delicious large speaker build. Love it!

There is no substitute for cubic inches!

Anyone care to comment on the size? I can go to up 140 liter per 15" woofer. I believe ChopShop did 5 cuft per woofer (135 liter). OR I can do 270-280 for a single 18".

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post #19 of 92 Old 01-31-2014, 07:16 PM - Thread Starter
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What about two 18" from Beyma: 18P80Nd. Specs seem great, wide frequency range and 100dB/watt. Ofcourse in MTM (more WTW) the distance between the center would be 86 cm (34"). 18" looks nicer with the SEOS-24™.

Price is reasonable when purchased in Spain: about €320 incl delivery.

Beyma_18P80NdE.pdf 334k .pdf file

BEF-NO initially used two 15P80Nd in his inConcert Miles LCR:

http://www.avsforum.com/t/1416004/bef-from-norway-diy-uncompromising-theater/30#post_22161723

Then he added a third 15" plus a dedicated midrange:

http://www.avsforum.com/t/1416004/bef-from-norway-diy-uncompromising-theater/120#post_23278790

As you will notice, I was all set to build that one, but the dispersion issues put me off. It is really only a 40° horizontal dispersion, not 80° as claimed for the TPL150H by Beyma.

Here's another fine example of a threeway version of the inCincert Miles:
http://www.hifisentralen.no/forumet/mitt-hi-fi-anlegg/71117-ntligen-hemma.html
He uses two x-over points to the woofers which he chooses from: 150 Hz (vocal) or 250 Hz (metal)
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post #20 of 92 Old 01-31-2014, 07:22 PM
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So would using a single 15" or even a single 18" woofer solve the center to center issues with lobbing on the Seos-24 with a compression driver, (be it a BMS-4594, or even a Radian 950BePB), that is crossed at 500hz or even 450hz?
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post #21 of 92 Old 01-31-2014, 07:48 PM
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That would "solve" the "problem". But I don't think its a problem at that frequency. The vertical spreads is probably a bigger advantage than the negative of lobing.

I'd go with 18s myself. As long as its free of any break up until 800hz and nothing to crazy until 1000hz or higher.
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post #22 of 92 Old 01-31-2014, 09:13 PM
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The AE TD-15S works well in 5ft^3 sealed. I believe the AE TD-18H works well in 5ft^3 ported, and is more efficient.

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post #23 of 92 Old 02-01-2014, 05:54 AM - Thread Starter
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The AE TD-15S works well in 5ft^3 sealed. I believe the AE TD-18H works well in 5ft^3 ported, and is more efficient.
AE is not on the European market hence the shipping, duties and VAT make it too expensive vs the EU brands. I guess they would cost about €500 each to me. Beyma, a Spanish brand are like €320 if bought at a Spanish webshop. And the 18P80Nd is certainly not the cheapest Beyma 18", but maybe the best for my goal.

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post #24 of 92 Old 02-01-2014, 06:01 AM - Thread Starter
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That would "solve" the "problem". But I don't think its a problem at that frequency. The vertical spreads is probably a bigger advantage than the negative of lobing.

I'd go with 18s myself. As long as its free of any break up until 800hz and nothing to crazy until 1000hz or higher.

I think the Beyma 18P80Nd is excellent. Frequency range is 25-4000 Hz and fs = 30 Hz. And 100 dB / 1 Watt efficient. So it goes both lower and louder than the already excellent 18Sound 15ND930 as far as I can tell.

Beyma_18P80NdE.pdf 334k .pdf file

Which tune would you recommend in a 5 cuft (135 liter) net volume for each of the drivers?

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post #25 of 92 Old 02-01-2014, 10:01 AM
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The specs might say 4000hz but I wouldn't let that thing make a whisper above 1khz. Looks good though.
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post #26 of 92 Old 02-02-2014, 07:46 AM
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Quote:
Originally Posted by jbrown15 View Post

How the heck does Jeff from JTR get away with using the even smaller XR1464 and crossing over the BMS 4593 so low in his 212HT's confused.gif

First we don't know (at least I've not seen it posted) what Jeff is doing with the crossover. The spec is fairly vague.

With that said, the BMS mid in home use is easily used down to 450hz. The rising distortion right at 450hz is basically nil once a filter is applied. Whether it is better crossed at 450 or up by 600 is a design choice with many factors.
Quote:
Originally Posted by tuxedocivic View Post

That would "solve" the "problem". But I don't think its a problem at that frequency. The vertical spreads is probably a bigger advantage than the negative of lobing.

I'd go with 18s myself. As long as its free of any break up until 800hz and nothing to crazy until 1000hz or higher.

I agree that the concerns about comb filtering are overblown in this case especially with a 450hz cross. It also depends on how steep the transfer function is at in this region.

Now if it were up to me, I'd use 4 12" woofers with two side by side above and two side by side below. This has multiple benefits. First it will control directivity a bit lower. Second, the CTC spacing is better which widens the vertical lobe a bit and further reduces MTM comb filtering. Finally, This should further reduce excursion versus equivalent 15s. This reduces IMD.

Of course the differences between a single 15, MTM 15s, quad 12s or MTM 18s are small especially in a home where none of the drivers will be taxed. What I'm saying is that it would be hard to tell them apart assuming equal implementation.
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First we don't know (at least I've not seen it posted) what Jeff is doing with the crossover. The spec is fairly vague.

With that said, the BMS mid in home use is easily used down to 450hz. The rising distortion right at 450hz is basically nil once a filter is applied. Whether it is better crossed at 450 or up by 600 is a design choice with many factors.
I agree that the concerns about comb filtering are overblown in this case especially with a 450hz cross. It also depends on how steep the transfer function is at in this region.

Now if it were up to me, I'd use 4 12" woofers with two side by side above and two side by side below. This has multiple benefits. First it will control directivity a bit lower. Second, the CTC spacing is better which widens the vertical lobe a bit and further reduces MTM comb filtering. Finally, This should further reduce excursion versus equivalent 15s. This reduces IMD.

Of course the differences between a single 15, MTM 15s, quad 12s or MTM 18s are small especially in a home where none of the drivers will be taxed. What I'm saying is that it would be hard to tell them apart assuming equal implementation.

I saw a thread on the Klipsch forum a while back where a guy used four Dayton Pro-10's in a CornScala build that he did. It looked like an awesome speaker!

So you are saying that any differences between a single 18", a MTM with 15" drivers or a quad 12" driver configuration would be small in a typical small room in a home theater environment?

I really like Scott's design with the quad JBL-2226's in each of his LCR's. That is probably huge overkill, but cool, none the less!
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post #28 of 92 Old 02-02-2014, 12:34 PM
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Yep, diminishing returns. Look at the shootout that included the Danley, Seaton, CBT and Noesis. Four very well designed speakers and nobody could even figure out which was which. There were even big design differences.

Adding woofer capacity is cool but frankly a single pro 15 isn't breaking a sweat from 80-400hz in even the craziest home setup. Two is nice, but the difference is so small because you are really only buying headroom. Yes, there is less excursion but you are going from maybe 1mm to .5mm.

Of course there are other potential benefits (and downfalls) to more midwoofers.

Much of this is like a guy with a 1000hp drag car fighting for 2hp. That might make sense because it is a competitive environment but with speakers we are strictly subjective and these tiny differences get overshadowed by larger factors like room interaction.

Of course it isn't an either or proposition, but once you get capability in the range of dual high end pro 15" mid basses the only way to improve is by working on the room. It is like that 1000hp guy adding 200hp but he just spins the tires and runs the same time (and probably no quicker than when he was at 500hp).
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post #29 of 92 Old 02-02-2014, 01:20 PM
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Originally Posted by coctostan View Post

Adding woofer capacity is cool but frankly a single pro 15 isn't breaking a sweat from 80-400hz in even the craziest home setup. Two is nice, but the difference is so small because you are really only buying headroom. Yes, there is less excursion but you are going from maybe 1mm to .5mm.
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+1. If there is a way to improve the overall result it's not with a larger woofer, it's by using multiple smaller woofers, vertically stacked, for wider horizontal dispersion where you want it, narrower vertical dispersion where you don't. The main thing you accomplish with going larger is to require a lower crossover. The same applies to using multiple woofers that aren't vertically aligned.

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post #30 of 92 Old 02-02-2014, 04:04 PM
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Originally Posted by Bill Fitzmaurice View Post

+1. If there is a way to improve the overall result it's not with a larger woofer, it's by using multiple smaller woofers, vertically stacked, for wider horizontal dispersion where you want it, narrower vertical dispersion where you don't. The main thing you accomplish with going larger is to require a lower crossover. The same applies to using multiple woofers that aren't vertically aligned.

Bill, would you mind explaining a little bit about where you would want narrower vertices dispersion? Also, would duel woofers that are side by side not help with both horizontal dispersion and reduce some of the lobbing associated with vertically stacked woofers?
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