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Old 07-31-2015, 07:24 AM - Thread Starter
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DIY Front Soundstage build - 3-way Triple 12 Inch, Beyma TPL-150 AMT

**** EDIT: Here is the Final Result! ****



















And the OmniMic Response in Room with all 3 speakers overlaid.






-----------------------------------------

**** Original Thread starts here:

Hey all.

This is the first thread I have ever created, I have been lurking around here a while and spending a lot of time in the Projector threads, now I have my vision set up (Sony 300ES / 120") and I plan to move on to my third DIY audio project and post some thoughts on the process here as I go.

This one is going to slowly begin the process of replacing my home theater speakers.

Some back story of my journey so far...

Here are a couple pics of my system...







So my first build was a PC speaker replacement. I had the amazing Logitech X530 for over 10 years as my PC sound, eventually got fed up with it and decided to tackle a simple 2-way project and 10" sub build to gain some knowledge about design after loitering the DIY forums for so long. They system consists of a Peerless 830860 5 1/4inch woofer and Vifa XT25 ring radiator tweeter. Crossing over 2nd order at 2800hz, They sound fantastic and I am just about to finish the veneer process with those after just being plain lazy with finishing that part for about a month. For the sub I am using a sealed enclosure with an SB Acoustics 10'' SB29SWNRX-S75-6 Woofer.

Here are some quick pics of the PC Speakers I built, you can see a vented 8 inch sub there, it also had a peerless 8 inch SLS woofer but it was crap, I also had a 100w Yung sub plate amp which literally fried and burned after 30 minutes at 1/3rd volume. I wasn't happy with either so I pulled them out and went 10inch sealed with a 200w Dayton Sub amp.



And the replacement 10 inch woofer. Much better! Suitable for PC audio



Anyway I will post the finished product in a few days so you all can see, they are almost finished with veneering.

Next, my father wanted a new center channel speaker which can match his ESS AMT-3 speakers, They are 3-way with currently 2x Dayton ST-255-8 drivers up to 250hz and then an Eminence Alpha 6a up to 750hz and the Heil AMT taking over from there. This is how it is from the factory. We decided on using those same drivers, but he found an Eton ER4 AMT driver on Ebay and ordered that so I set out to build that crossover which is the same except the Eton was crossing over at a much safer 1800hz. Sucess! It sound amazing. By this point I have purchases SoundEasy and used that to design the crossover. I has previously used Bassbox Pro and Xover Pro 3 for my PC Speakers and grew frustrated quickly with its lack of options, however it is AMAZING for quickly bashing a box design together and thus I use Bassbox pro for designing the enclosure and move to SoundEasy for the crossover part.

This is how the crossover looks for my fathers center channel. (Sorry no photos of the actual speaker right now.) you can see the Eton has a natural roll off on the high end. And yes, the impedance drops to 2 at one point... One obstacle with my father blindly buying that AMT was the fact that is was only 88db/1Watt vs the other drivers being around 92db, so in order to bring the system to a respectable sensitivity it looks like thats why the impedance drops so low at that point. Not to worry though, my father is driving those speakers with 500watt mono blocks so it will be fine.



Ok so back to me...

Lets just say that I absolutely fell in LOVE with AMT's. The sound... just so airy, effortless and clear. Tough to describe it. I wanted to use them for my next build... So some research led me to Beyma and their line of drivers. The TPL-150H AMT is a horn loaded 102db/watt monstrosity. That will be my tweeter, The Beyma 12p80Ndv2 will be my mid speaker and I will use two Faital 12FH520 -16ohm Woofers for the low end. I should end up with an 8ohm ~100db/watt speaker out of those and it should hopefully have some incredibly powerful dynamics for music and film.

Here are some designs of the enclosure I am going for the final final design will be very close to this, just getting all the calcs down to mm perfect for the CNC cutting.













Here is the box model in Bassbox Pro.



I will get these CNC cut in the next week or so and begin measuring the drivers in their finished enclosures so I don't have to do any baffle calculations at crossover build.

So, the Beyma side of things arrived, The Faital woofers are shipping from Italy on Monday. I had to hear the AMT's so I quickly plugged them into my tweeter crossover on my PC speakers for a listen. Amazing!









Thanks for listening guys, will update this thread again as the journey continues.

Feel free to ask any questions, chime in with advice, I will definitely be asking for advice as I get close to the crossover build.

Cheers!

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Last edited by Javs; 02-11-2016 at 06:37 PM. Reason: Final Result Added
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Old 07-31-2015, 11:19 AM
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cool.

Listen. It's All Good.
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Old 07-31-2015, 11:46 AM
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This thread has "win" all over it.

I too am building some speakers with the Beyma TPL-150Hs, I couldn't believe how big they were!
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Old 07-31-2015, 12:35 PM
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Looks like a very capable set up, just curious as to the choice of the 12" mid since you have the other two twelves that are probably doing most of the mid bass duty?
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Old 07-31-2015, 06:45 PM - Thread Starter
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@gpmbc There are a few threads around about the best mids to pair with the TPL-150 and that driver more than consistently popped up as being a match made in heaven due to having an incredibly fast transient response and also being a large woofer the dispersion supposedly matched better than a smaller mid does.

http://diyaudio.com/forums/multi...tpl-150-a.html

http://diyaudio.com/forums/multi...tpl-150-a.html

The idea from this speaker came about from seeing what Stig Erik had done with the In Concert Miles and Duke speakers and wanting to replicate that but add a mid woofer and make it 3-way as Stig had commented that while those speakers were amazing he wished they had a dedicated mid bass driver...

Here are some pics of the Miles/Duke and also a 3-way version using I think a 10inch driver.









The driver which was used in the Duke models a little lower extension than the Beyma 12p80Nd however as a mid it is not nearly as flat:

12p80NdV2



12p1000Nd



The crossover is likely to be in the neighborhood of 250/350 & 1800hz for the 3-way. The two Faital drivers I ended up deciding on modeled far superior to any of the Beyma woofers on offer for lower range speakers. The low end extension had a much better curve and less of a stepped shelf for the enclosure size I wanted to use. And the fact that the woofers are 16 ohms each that will net me 8 ohms and around 99db/watt when I pair them together rather than around 3ohm.

I want these to have force and be flat as possible from about 35-40hz and up. I will in the future build new large subs to match them but I would need to move house before that's even possible without being evicted.

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Old 07-31-2015, 06:55 PM
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Awesome man, thx for the informative response I'll be following along.
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Old 07-31-2015, 07:58 PM

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what do you have for surround duty?
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Old 07-31-2015, 09:31 PM - Thread Starter
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@thebedbeard Well, at the moment just the same speakers I am using in my current setup which are 7 Krix KDX speakers. And a Krix Seismix 3 for a sub.

Essentially it is these:

http://krix.com.au/acoustix-mk2.html
http://krix.com.au/seismix3.html

Though my mains don't have front facing ports, they are rear facing and my tweeter is not a ring radiator tweeter as shown in this image. But more or less same specs; its an earlier model of the same line. They have been fantastic and the system currently is a joy to listen to, but not long after I complete this new front sound stage I will have a look at building the other four surround speakers using the Beyma TPL-150 as the tweeter. I might look at finding a good 10 inch mid or even an 8 inch which can give me at least 60/80 hz up to 1800hz comfortably, end up with around 98-99db/watt sensitivity and pair it up with the Beyma AMT. That way they will be tonally matched with the fronts and the subwoofer will take care of the lower freq duties. The Beyma TPL-150 is an incredible tweeter and is VERY revealing, so it will be very noticeable if the rears don't have them, the sound is totally different and almost seems muffled by comparison.

These front speakers though, I wanted them to be as full range as possible and when time comes to listen to music in stereo they really hold their own as musical stereo speakers. I am a firm believer in the front three speakers being identical so the center is exactly the same drivers and box internal volume to match the left/rights. Hell all speakers should be identical in an ideal world which is what I have now but that would turn into a very expensive project.

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Old 07-31-2015, 09:42 PM - Thread Starter
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Oh, one thing I did want to ask for advice on but forgot was for thoughts the driver layout on the tower speakers..

At the moment I was thinking of having the LF drivers as the bottom two drivers, then the AMT and then the mid range speaker at the top, the mid range and the AMT would be in its own internal sealed enclosure. This way when in the seated position the AMT should be at about ear height which is optimal as we all know they don't have a very broad vertical dispersion.

But as you can see the center channel at the moment has to sit below my projector screen, which will be just above knee height. And if you look at that layout of the center, the mid range speaker is below the AMT.

Are there any thoughts or pros/cons on the current layout idea of W/W/T/M?

Do you think to match the center better it should be W/M/T/W?

I am not sure of any negative effects of having the LF drivers separated by that much, since they are crossing at around 250/350hz and its probably about 65cm from voice coil to voice coil if they were laid out like that I'm not sure...

350hz has a 980mm wavelength for eg... does that mean I would be in the clear if I went that route?

Cheers!

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Old 07-31-2015, 10:06 PM - Thread Starter
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Just while we wait for more news on the actual AMT build here are a few shots of my only just veneered PC speakers. Just after the first coat of Scandinavian Oil. Please excuse my amateur routering skills! When all the drivers, ports and binding posts are installed they look great.











PSA, if anybody wants to know a great router bit for flush trimming a part of your speaker which has a very shallow flush mount hole such as a tweeter then use this! Its #51204

http://toolstoday.com/showProduc...ProductID=5117



***EDIT - Here are the finished small desktop speakers!







ORIF, cuzed2 and EarlK like this.

JVC X9500 (RS620) | OZTS 120" 16:9 | Marantz AV7702 MkII | Emotiva XPA-7 | RMB-1555B | DIY Modular Towers | DIY MTM TPL-150 Surrounds | DIY Atmos Modules | DIY 18" Subs
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Last edited by Javs; 08-07-2015 at 10:23 PM.
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Old 08-07-2015, 05:47 PM
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Quote:
Originally Posted by Javs View Post
Oh, one thing I did want to ask for advice on but forgot was for thoughts the driver layout on the tower speakers..

At the moment I was thinking of having the LF drivers as the bottom two drivers, then the AMT and then the mid range speaker at the top, the mid range and the AMT would be in its own internal sealed enclosure. This way when in the seated position the AMT should be at about ear height which is optimal as we all know they don't have a very broad vertical dispersion.

But as you can see the center channel at the moment has to sit below my projector screen, which will be just above knee height. And if you look at that layout of the center, the mid range speaker is below the AMT.

Are there any thoughts or pros/cons on the current layout idea of W/W/T/M?

Do you think to match the center better it should be W/M/T/W?

I am not sure of any negative effects of having the LF drivers separated by that much, since they are crossing at around 250/350hz and its probably about 65cm from voice coil to voice coil if they were laid out like that I'm not sure...

350hz has a 980mm wavelength for eg... does that mean I would be in the clear if I went that route?

Cheers!
With the two woofers at the bottom, it does give max height for the tweet and as you mentioned vertical dispersion is its weakest point. What if the midrange driver and tweeter had their own self contained enclosure (essentially a box sitting on top of the midbass drivers)? If mounted high, that could give you the option to angle the mid/high section down a few degrees and possibly negate most of dispersion issues. This would just apply to the L and R speakers. Just a thought.
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Old 08-07-2015, 10:11 PM - Thread Starter
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Quote:
Originally Posted by gpmbc View Post
With the two woofers at the bottom, it does give max height for the tweet and as you mentioned vertical dispersion is its weakest point. What if the midrange driver and tweeter had their own self contained enclosure (essentially a box sitting on top of the midbass drivers)? If mounted high, that could give you the option to angle the mid/high section down a few degrees and possibly negate most of dispersion issues. This would just apply to the L and R speakers. Just a thought.
Hmm I see what you're saying. I think that's not too dissimilar to the very tall white speakers I posted earlier in this thread. The complexity of the build would shoot up quite a few notches like this. Im not sure I am ready for that kind of angling. Although I am getting everything CNC cut.

As it stands with this design, even so with the one you are suggesting the AMT will actually be exactly at ear height anyway no matter which layout I go with. Though the mid woofer will be above it with my current design. If I were to go WMTW the tweeter would still be exactly at ear height but the mid woofer would be slightly below it... either option puts the mid either 30cm above my ear level or 30cm below it.

Which is the lesser of two evils?

Angling it by about 10 degrees or so in its own box section could be a smart move though. This would ensure people shorter than me in the seated position (My wife) will still get the AMT aimed right at ear height, which is the much more critical driver in terms of needing to be pointed exactly in the right direction. However the mid driver crossing over at 1800hz will be creeping into that territory too at certain frequencies though that was one of the things about being a 12 inch mid was supposed to overcome, should be a rather wide dispersion right?

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Old 08-08-2015, 07:45 AM
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Quote:
Originally Posted by Javs View Post
Hmm I see what you're saying. I think that's not too dissimilar to the very tall white speakers I posted earlier in this thread. The complexity of the build would shoot up quite a few notches like this. Im not sure I am ready for that kind of angling. Although I am getting everything CNC cut.

As it stands with this design, even so with the one you are suggesting the AMT will actually be exactly at ear height anyway no matter which layout I go with. Though the mid woofer will be above it with my current design. If I were to go WMTW the tweeter would still be exactly at ear height but the mid woofer would be slightly below it... either option puts the mid either 30cm above my ear level or 30cm below it.

Which is the lesser of two evils?

Angling it by about 10 degrees or so in its own box section could be a smart move though. This would ensure people shorter than me in the seated position (My wife) will still get the AMT aimed right at ear height, which is the much more critical driver in terms of needing to be pointed exactly in the right direction. However the mid driver crossing over at 1800hz will be creeping into that territory too at certain frequencies though that was one of the things about being a 12 inch mid was supposed to overcome, should be a rather wide dispersion right?
At 1.8khz the 12 will be beaming like crazy.....it will be at 90deg at about 1.1khz. Also, you're probably looking at greater than 1wl of separation. Just guessing on the driver spacing, but you're looking at the vertical null spacing of like +/-18deg. I think that calc assumes an omnidirectional source, and depending on the design axis it will likely be narrower than that.

From a directivity standpoint that Beyma would be better paired with an 8" driver....or even better than that a 6. The Beyma literature says it's good to 1khz but I've read over and over that people don't like them that low for a sound quality app. I think it's kind of a strange beast, being so high eff and coming from a pro company, that it really doesn't pair well with anything for pattern control while keeping the sensitivity up in a passive design. You might try a lower xo and see what you think. I would like to hear them someday........cool build!
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Old 08-08-2015, 09:07 AM - Thread Starter
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Quote:
Originally Posted by Nate Hansen View Post
At 1.8khz the 12 will be beaming like crazy.....it will be at 90deg at about 1.1khz. Also, you're probably looking at greater than 1wl of separation. Just guessing on the driver spacing, but you're looking at the vertical null spacing of like +/-18deg. I think that calc assumes an omnidirectional source, and depending on the design axis it will likely be narrower than that.

From a directivity standpoint that Beyma would be better paired with an 8" driver....or even better than that a 6. The Beyma literature says it's good to 1khz but I've read over and over that people don't like them that low for a sound quality app. I think it's kind of a strange beast, being so high eff and coming from a pro company, that it really doesn't pair well with anything for pattern control while keeping the sensitivity up in a passive design. You might try a lower xo and see what you think. I would like to hear them someday........cool build!
Just wondering what tool you use to figure the beaming stats? Wondering how you arrived at 90deg @ 1.1khz. My knowledge in that area is still quite limited. Its interesting, I got through a 30 page or so thread over at DIY forums of that 12 inch being sich a great match to the Beyma AMT. I also read of somebody having no issues at up to 40deg off axis at 1600hz with that combo.

Is that what would happen with 'beaming'? You would get a bad off axis response at certain freqs with that driver and essentially creating a null at particular freqs until the AMT comes in?

What would the beaming be at 1600hz? Sounds like 1600hz is the lowest most people are crossing at and not stressing out the AMT so I will go with that.

As far as the placement goes 1600hz wavelength is around 8.5inches or around 22cm, that is pretty much the distance between the centre of the 12's voice coil to the centre of the Beyma AMT in my model. But given the nature of the AMT It only really has to hit the edge of its ribbon right? Is that still bad?

I already have the woofers so probably not really going to change them out at this point.

I think this is supposed to be a measured polar response of the Beyma TPL-150H if thats worth anything.



I appreciate all the help and knowledge people. Its all a learning process for me and a journey. There has to be some trial and error involved that really is the best way to learn.

JVC X9500 (RS620) | OZTS 120" 16:9 | Marantz AV7702 MkII | Emotiva XPA-7 | RMB-1555B | DIY Modular Towers | DIY MTM TPL-150 Surrounds | DIY Atmos Modules | DIY 18" Subs
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Old 08-08-2015, 11:22 AM
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A real basic way to determine where a cone driver is at 90deg is to take the speed of sound divided by the diameter of the driver.....13500/12=1125. This is a decent ballpark to work with. The pattern is progressively narrowing above this point (and progressively widening below dictated by driver size and baffle) and at 1.8khz the pattern of the woofer will be significantly narrower than the Beyma which will be pretty wide. At 1.6k it will be closer but there will still be a discontinuity. Many don't pay attention/care about the polar response. I personally do and research suggests that a smooth off-axis response at the xo is important. That said you have what you have at this point, and that doesn't mean that it won't sound good. A wide listening room or heavy room treatment might mitigate the effects of the directivity change between drivers.

I think you may be right about using the bottom of the AMT diaphragm to calculate ctc.

I'd say more but I gotta go.....
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Old 08-08-2015, 03:19 PM
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PC speakers looks great!
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Old 08-08-2015, 10:24 PM - Thread Starter
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PC speakers looks great!
Thanks man!

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Old 08-08-2015, 10:59 PM
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Quote:
Originally Posted by Nate Hansen View Post
A real basic way to determine where a cone driver is at 90deg is to take the speed of sound divided by the diameter of the driver.....13500/12=1125. This is a decent ballpark to work with. The pattern is progressively narrowing above this point (and progressively widening below dictated by driver size and baffle) and at 1.8khz the pattern of the woofer will be significantly narrower than the Beyma which will be pretty wide. At 1.6k it will be closer but there will still be a discontinuity. Many don't pay attention/care about the polar response. I personally do and research suggests that a smooth off-axis response at the xo is important. That said you have what you have at this point, and that doesn't mean that it won't sound good. A wide listening room or heavy room treatment might mitigate the effects of the directivity change between drivers.



I think you may be right about using the bottom of the AMT diaphragm to calculate ctc.



I'd say more but I gotta go.....

Just a thought, he is using the TPL-150H which is a horn loaded version of the TPL-150. This should limit dispersion of the tweeter at the intended crossover frequency and may provide a better directivity match with the 12" midrange at the intended crossover frequency of 1600Hz. With this combo I have read some having excellent results with up to an 1800Hz crossover point.

I am building a set of speakers with the TPL-150H and an Acoustic Elegance TD-12M. My intended crossover point will be at 1800Hz. I will be using a MiniDSP for crossover duty though, so I will probably play with it and see what works.
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Old 08-08-2015, 11:26 PM - Thread Starter
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Just a thought, he is using the TPL-150H which is a horn loaded version of the TPL-150. This should limit dispersion of the tweeter at the intended crossover frequency and may provide a better directivity match with the 12" midrange at the intended crossover frequency of 1600Hz. With this combo I have read some having excellent results with up to an 1800Hz crossover point.

I am building a set of speakers with the TPL-150H and an Acoustic Elegance TD-12M. My intended crossover point will be at 1800Hz. I will be using a MiniDSP for crossover duty though, so I will probably play with it and see what works.
Hey, I have read that also... I was worried for a second there. I would love to know how you go with your build progression if you get to yours before mine. I am probably a couple weeks away at least before boxes are fully built and I will be ready to nail down crossover values. So please do post info either here or a new thread when you get to your build, very interested to see how you go with your 1800hz cross over point!

I have also read our 12 inch woofers are supposedly very very close in likeness so it should be interesting.

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Old 08-09-2015, 07:57 AM
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Originally Posted by trevordj View Post
Just a thought, he is using the TPL-150H which is a horn loaded version of the TPL-150. This should limit dispersion of the tweeter at the intended crossover frequency and may provide a better directivity match with the 12" midrange at the intended crossover frequency of 1600Hz. With this combo I have read some having excellent results with up to an 1800Hz crossover point.

I am building a set of speakers with the TPL-150H and an Acoustic Elegance TD-12M. My intended crossover point will be at 1800Hz. I will be using a MiniDSP for crossover duty though, so I will probably play with it and see what works.
Yep, I get that it's on a horn, and that certainly is better than the version without. Not to keep beating this horse, but I'm a directivity freak and I think a lot of people downplay it's importance. The op did seem to be concerned with the match up. I've included an actual 0-20-40° measurement.....credit for the data goes to Brandon (augerpro).

I did a quick course sim of a 12" in driver on an infinite baffle as well. The measured result and the sim aren't quite as bad as I was envisioning. Looks like it's at 50-60° at 1.6-1.8khz. Again, I'm NOT saying that this won't sound good or that I'm trying to deter you from what you're doing and it will be cool to see how these turn out.
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Old 08-09-2015, 08:07 AM
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This thread feels like a review of my thoughts a long time ago.

I still havent made my final speakers yet, due to other personal matters, but look forward to your progress. Hopefully I will finally figure out if I am going to build a 3 way or 2 way setup after seeing your progress.
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Old 08-09-2015, 09:07 AM - Thread Starter
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Originally Posted by Nate Hansen View Post
Yep, I get that it's on a horn, and that certainly is better than the version without. Not to keep beating this horse, but I'm a directivity freak and I think a lot of people downplay it's importance. The op did seem to be concerned with the match up. I've included an actual 0-20-40° measurement.....credit for the data goes to Brandon (augerpro).

I did a quick course sim of a 12" in driver on an infinite baffle as well. The measured result and the sim aren't quite as bad as I was envisioning. Looks like it's at 50-60° at 1.6-1.8khz. Again, I'm NOT saying that this won't sound good or that I'm trying to deter you from what you're doing and it will be cool to see how these turn out.
Hey so thanks very much for this info. I appreciate it.

So your data, that's from a TD12M measurement isnt it? I have seen that over at DIY Audio forum. Would that data vary at all for my speaker? I have the V2 version of the 12p80 also which does extend quite a bit higher than the previous revision and has a lot less distortion... Not sure if those numbers would change based on that.

And if I get this right, you are saying 1600hz crossover would be around 60 degrees, the AMT has an 80/40 horn on it, would I be right in assuming the beyma would be at 80 degrees at that point? Is that really so bad?

There is also this dispersion prediction (based on the TD12M though) at DIY Audio too:

http://diyaudio.com/forums/multi...project-3.html



Is that a bad prediction?

They other thing is, my room and these speakers are going to be toed in and facing the center of a couch with 3 seats, that will be the listening position. 3 seats wide. My setup is on the long walls of a rectangular room so on one side I have curtains and glass, the other side has 5m of air before it hits the next wall. The rear of my room is treated with about 8 acoustic panels and there is my bookshelf probably acting as a diffuser too.

I know I did say I wanted the Left and Right channels to be as best as they can be for stereo playback, but what are we actually talking about here? I'm just trying to get a grip on what this data means. You say they probably wont sound bad given these issues, but my question is, if I am sitting in the listening position hearing these speakers, and the towers are facing me and anyone who is enjoying the music or film with me is sitting right next to me and essentially by extension they would be on axis to the speaker, what detrimental effects will I experience? Are we talking purely off axis here? What is 60 degrees? Is that 30 degrees to either side of the speaker? If that's the case and the Beyma AMT is at 80 degrees (I have already listened to the AMT where they will live aimed at the listening position and have experienced its dispersion) is an extra 10 degrees side to side really a horrible thing? Or am I interpreting this data incorrectly?

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Old 08-09-2015, 11:39 AM
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Yeah, 60deg is +-30deg. Like I said the pattern doesn't narrow as much on the TD12 as I was thinking it would, and with the right xo the blend off axis could be fairly smooth I think. I'm a stickler for a smooth off-axis transition through the xo region, but in reality you're fairly close. The main thing is that there aren't any huge changes off axis, like you might see with an 8" midbass and a 1" dome tweeter. In that configuration the 8" would be pretty directive at the xo while the dome is omni or near omni.

You're right that quibbling over a 10deg mismatch in the xo isn't a huge deal. Speaker design is all about compromise and you've certainly got some nice parts to work with!

A smooth off-axis response for a loudspeaker is important for a couple reasons. One, if you have a wide seating area a smooth polar will ensure that all seats are getting a similar facsimile of the axial response for the main lp. It's also important for the reflected energy to not have excess at certain frequencies that a speaker with a highly irregular polar response would have. In a small room the reflected sound has an effect on imaging, spaciousness, and intelligibility afaik; a smooth polar will help keep the spectrum of the reflections similar to that of the axial response which will improve sq.

Don't mind me, carry on
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Old 08-09-2015, 12:42 PM
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Quote:
Originally Posted by Nate Hansen View Post
Yeah, 60deg is +-30deg. Like I said the pattern doesn't narrow as much on the TD12 as I was thinking it would, and with the right xo the blend off axis could be fairly smooth I think. I'm a stickler for a smooth off-axis transition through the xo region, but in reality you're fairly close. The main thing is that there aren't any huge changes off axis, like you might see with an 8" midbass and a 1" dome tweeter. In that configuration the 8" would be pretty directive at the xo while the dome is omni or near omni.

You're right that quibbling over a 10deg mismatch in the xo isn't a huge deal. Speaker design is all about compromise and you've certainly got some nice parts to work with!

A smooth off-axis response for a loudspeaker is important for a couple reasons. One, if you have a wide seating area a smooth polar will ensure that all seats are getting a similar facsimile of the axial response for the main lp. It's also important for the reflected energy to not have excess at certain frequencies that a speaker with a highly irregular polar response would have. In a small room the reflected sound has an effect on imaging, spaciousness, and intelligibility afaik; a smooth polar will help keep the spectrum of the reflections similar to that of the axial response which will improve sq.

Don't mind me, carry on
This is still great information! Thanks for the discussion.
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Old 08-09-2015, 04:58 PM - Thread Starter
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DIY Front Soundstage build - 3-way Triple 12 Inch, Beyma TPL-150 AMT

Quote:
Originally Posted by Nate Hansen View Post
Don't mind me, carry on

Again thanks so much for chiming in, I think I have a much better understanding of what you are saying now. I will do some measurements and see if I can get away with 1500/1600hz for those reasons.

I definitely understand where you are coming from here!

Wow so an 8 inch and dome tweeter have even larger problems?? Didn't know that. Sounds like Im in for a good sounding speaker if I can get the crossover nice and smooth.

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Old 08-09-2015, 05:19 PM
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Glad to help. I DON'T want to sound like a know it all (because I don't!) but I try to relate my experience to the theory and research that I've found. And when I'm wrong, I'm wrong . If you find the psychoacoustic stuff interesting I'd suggest skipping the middle man and checking out "Sound Reproduction" by Floyd Toole.
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Old 08-09-2015, 08:50 PM - Thread Starter
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Thanks Nate.

For those interested, I just watched a 1 hour keynote from Mr Floyd Toole summarizing his book. VERY interesting. Enlightening.


Looks like I will be OK if I can get the directivity as close as possible at the crossover without it being a huge change... So sounds like I will be playing around with a 1400-1600hz crossover on the AMT. I don't think I will ever run these speakers too much over 100db anyway unless I am keen on damaging my ears so hopefully the AMT wont fare too bad at 1400hz if that's what turns out to be the best match.

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Old 08-09-2015, 09:33 PM
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So sounds like I will be playing around with a 1400-1600hz crossover on the AMT. I don't think I will ever run these speakers too much over 100db anyway unless I am keen on damaging my ears so hopefully the AMT wont fare too bad at 1400hz if that's what turns out to be the best match.
I liked them crossed closer to 2K. Although measurements were fine at lower frequencies, subjectively I preferred a higher crossover point.
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Old 08-09-2015, 09:56 PM - Thread Starter
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I liked them crossed closer to 2K. Although measurements were fine at lower frequencies, subjectively I preferred a higher crossover point.
Yeah 1800hz would be the max I am willing to do given the size of the mid I am using (Beaming - above discussion) and also going by what many arrived at being the best for the mid/AMT combo I have.

Do you have the same mid as me? The 12p80 is supposed to have utterly amazing transients. Thats where the 1800hz number came from. That combo. The TD12M is supposedly pretty close too.

I will go lower if beaming seems to have a major detrimental effect at 1800hz. One person has measured and said no major issues with 40degree of axis measurements at 1800hz with that combo but will have to see.

OmniMic kit just arrived. Just need to get these boxes built now and its game on with in box measurements, and we will really see what is what.

Will definitely be posting a bunch of graphs here once I get the hang of using it and have built my boxes. Will definitely get feedback from everyone before deciding on a final number.

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Old 08-09-2015, 09:58 PM - Thread Starter
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I liked them crossed closer to 2K. Although measurements were fine at lower frequencies, subjectively I preferred a higher crossover point.
Hang on you built Mikes baffle wall crossover right? He ended up at 1800hz yes? Did you see any beaming issues with his setup?

He has the TD12M yes?

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