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Discussion Starter #1 (Edited)
***EDIT***

Here is the final product! Ended up with MTM config, 1250hz crossover 12db/oct.




















-------------Thread Start-------------

Hey Guys,

Well my front sound stage build is all done and wrapped now... Been listening to them for the past month or so in bliss. Everything sounds great... Except they make my non pro-audio rear speakers sound like crap.

SO, in the interest of timberal matching, and feeding the DIY bug I am about to begin my build for the 4x rear speakers to complete the 7 channel sound bed. So I will have TPL-150H AMT Tweeters all around me.

This is also going to act not only as my rear speaker but also as a prototype build to perhaps look at selling these as a kit or offer them as finished speakers locally here in Australia. Other people would probably consider these very useful for a main sound stage. But with my mains, these should compliment very nicely.

I am going for two way. Dual 8inch Faital 8PR200 woofers, and the TPL-150H AMT.

1800hz crossover point. 8ohm nominal. 98db/Watt Sensitivity.

Spec Sheets:

http://www.usspeaker.com/beyma tpl150h-1.htm

http://www.faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101030200


Here is the design I have arrived at and the dimensions. I am looking at a box which has a 3db rolloff of 50hz. Flat to 80hz.

Everything will be cut on a CNC machine. I have designed it so it should be easy to cut more and what boxes together in minimal time with good strength. 25mm MDF throughout. These ones are just going to be sprayed with Duratex but hopefully the finish and texture will come out quite nice. I really like how the baffles turned out on my L/C/R speakers with the sprayed finish.



More to come soon! I will try to document this build a little better than my last one.
 

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Great choice of components. I was looking at doing the same setup but was unable to get the 8's so that went out the door. Look forward to how this progresses.
 

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Discussion Starter #5
The crossover would be too high due to the center-to-center distance of the 8's

You're right. How far off am I? On my phone at the moment Ill check the maths when I get home.

I could run the AMT as low as 1400/1500... Ive heard it and its fine. If I did that I could make a little chamber for it and take the back plate off. From what I read there is a little resonance which originated from the backplate if you crossover too low.

Failing that Ill look at 2.5 way and loose a little sensitivity.
 

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Discussion Starter #6
So I am thinking I will move forward with a 2.5 way scenario.

Is there any reason to think the current box design will not work well with a 2.5 way?

The 8 which will become the LF/Mid combo I am thinking will go above the AMT.

Thats somewhat similar to my current LCR speakers, the mid is on top.

Failing that, I could do it this way, though I am not super fond of the 'visual' aspect of this design. If the two designs would yield a pretty similar response with no adverse effects I will go with the design I posted originally.

I am guessing the below design would yield a bit more of an airy treble range to it.

This is for HT application though so I am kind thinking the mid on top to match my larger speakers will 'sound' more like a match.

Thoughts?

 

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Discussion Starter #8 (Edited)
Javs' Rear Speaker Project - Faital 8PR200 & Beyma TPL-150H

I had thought about a dual 8" system but went with a single 10", the TD10M and love it. I also didn't have to deal with crossing the lower unit at a different frequency that an upper 8. The TD10M is really efficient. It is a 4 ohm unit. I have active crossovers.



This is the thread from DIYaudio. The 8 you are looking to use go very mixed feedback for me. I hope this helps.



http://www.diyaudio.com/forums/multi-way/252562-ae-td10m-1-two-faital-8fh200-seos-10-bms-4550-a.html

Thanks

I wont use that brand its too expensive for me in Australia especially considering the prices I get from Beyma and Faital direct.

Already have all the drivers in hand.

I sent the top design off the the CNC shop.

Going with 2.5 way.

Ill update with box building and measurements.
 

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Can you consider a single fold MLTL tuning for the woofers, that may help extend the LF corner and make these full range speakers for 2 channel setup?

Sent from my GT-I9505 using Tapatalk
 

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Discussion Starter #10
Can you consider a single fold MLTL tuning for the woofers, that may help extend the LF corner and make these full range speakers for 2 channel setup?

Sent from my GT-I9505 using Tapatalk
I would totally consider that if I made this into a taller tower speaker which I almost did. Its more an extreme bookshelf speaker haha.

This is I guess 90% for my own needs obviously and 10% prototyping for possible set ups to offer to people in Australia if I get it right.

I definitely did not want towers for rears. A taller version with the lower woofer having a bit more cabinet area to work with would be a great idea for another variation on this config. The fs on this driver is 70hz though, so not sure how well it would do in a full range configuration.

The concept was make a speaker which would be great to 60/80hz crossover in a HT environment and hopefully great for music too.

As they are now, they will be 50hz -3db point and 40hz at -8db.

So I guess with a little EQ like Audyssey or something you would theoretically get them flat to 40hz if you wanted. Though I would recommend a pretty good roll off at 50hz as cone travel starts flying up under the tuning freq and you run out of xmax at 45hz if you fed them 400watts RMS (2 woofers).

100Watts of power would see that problem go away though and you would be fine for displacement at any freq. 100 watts would net you 115db though so that's more or less reference anyway.
 

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Hi!
what are the avantages of putting 2 x 8 inches woofers vs only 1??? and why replacing them with 1x 10 inches instead of 2?? thanks! cheers
 

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You're right. How far off am I? On my phone at the moment Ill check the maths when I get home.

I could run the AMT as low as 1400/1500... Ive heard it and its fine. If I did that I could make a little chamber for it and take the back plate off. From what I read there is a little resonance which originated from the backplate if you crossover too low.

Failing that Ill look at 2.5 way and loose a little sensitivity.
How is that sensibility calculated passing from a 2 way to a 2.5 way? thanks
 

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Discussion Starter #14
How is that sensibility calculated passing from a 2 way to a 2.5 way? thanks

It would actually be the same sensitivity in theory doing 2.5 way as the .5 way woofer will essentially over come the baffle step loss.

Here is an example (not my crossover)

 

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Discussion Starter #15
Javs' Rear Speaker Project - Faital 8PR200 & Beyma TPL-150H

I'm interested into having more infomration about how do you arrive to this conclusion, can you please explain it a bit?



thanks

For MTM to work properly and not have some high amount of lobing issues the center to center distance from the woofers needs to be as short as possible. One half wavelength is preferred. One wavelength is ok but not optimal.

But my design if I were to use two way MTM as pointed out by a forum member would have been too spread out and would actually be over two wavelengths in distance from each other at the crossover freq.

2.5 way gets around the lobing as one woofer is tapering off earlier than the other and by the time you hit the crossover freq to the tweeter the first bass woofer is almost gone completely. See reply above for what that looks like.
 

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Discussion Starter #16
Javs' Rear Speaker Project - Faital 8PR200 & Beyma TPL-150H

Hi!

what are the avantages of putting 2 x 8 inches woofers vs only 1??? and why replacing them with 1x 10 inches instead of 2?? thanks! cheers

Personally I wanted 2 8inch drivers, that was a design choice. Simple as that. I am not a huge fan of single woofer speakers visually.

I already have the drivers in hand so I am not interested in peoples suggestions on others as I already did some research and am wanting to try out the 8 inch Faitals. They are supposed to be great units.

10 inch drivers add width to the speaker which I was not interested in doing not to mention extra cost.

One reason I chose two is because the Beyma AMT sensitivity is 102db/watt.

One 8 inch driver is 95db. You have two and its 98db/watt in sensitivity so its a closer match to my design goal of making a speaker as close to 100db/watt as possible to match my mains which are already 100db/watt.
 

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Personally I wanted 2 8inch drivers, that was a design choice. Simple as that. I am not a huge fan of single woofer speakers visually.

I already have the drivers in hand so I am not interested in peoples suggestions on others as I already did some research and am wanting to try out the 8 inch Faitals. They are supposed to be great units.

10 inch drivers add width to the speaker which I was not interested in doing not to mention extra cost.

One reason I chose two is because the Beyma AMT sensitivity is 102db/watt.

One 8 inch driver is 95db. You have two and its 98db/watt in sensitivity so its a closer match to my design goal of making a speaker as close to 100db/watt as possible to match my mains which are already 100db/watt.
Many thansk for the answers...what soft are you using to simulate the speakers?
 

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Discussion Starter #18
Many thansk for the answers...what soft are you using to simulate the speakers?
Bassbox Pro for ideas and box modelling before building. OmniMic to measure when box is built, SoundEasy to model crossover and simulate/tweak.
 

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I'm interested into having more information about how do you arrive to this conclusion, can you please explain it a bit?

thanks
The rule of thumb is to not exceed a 1-wavelength center-to-center driver spacing at the crossover frequency. When two drivers make the same frequency you divide 13560 by the number of inches between them. If the center to center distance of two 8" drivers with an 8" tweeter between them is 17" then 13560/17 = 800hz for a decent crossover. That's too low for that AMT. For a 2.5 system using those drivers, 13560/9 would yield a 1500hz cross to the tweeter and 340hz or so is where you can roll out the lower 8" assuming a 38" center tweeter height.
 
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