A box is a box, right?

[Benni777]

This may be a dumb question but I am currently building a sealed center channel speaker and will be working towards the possible transmission line towers thereafter.

Question I have is, I am given the standard box design " just a rectangle box". Now in my mind I should be able to change this design to any shape AS LONG AS the internal box volume does not change, correct? (in my case a rectangle vs a trapezoid)

As for a ported or transmission line tower, this may be a bit different and would require a bit more calculated math but I would think the same applies, box volume and port length/width/height staying the same then we should be good to go.

As a visual, the standard box for the center is 8"H x 17"W x 10"D. I would be changing to a front baffle of 9"H x 19"W & rear of 7"H x 15"W, depth stays the same.

Your thoughts, opinions, ideas?

 

[TLS Guy]

This may be a dumb question but I am currently building a sealed center channel speaker and will be working towards the possible transmission line towers thereafter.

Question I have is, I am given the standard box design " just a rectangle box". Now in my mind I should be able to change this design to any shape AS LONG AS the internal box volume does not change, correct? (in my case a rectangle vs a trapezoid)

As for a ported or transmission line tower, this may be a bit different and would require a bit more calculated math but I would think the same applies, box volume and port length/width/height staying the same then we should be good to go.

As a visual, the standard box for the center is 8"H x 17"W x 10"D. I would be changing to a front baffle of 9"H x 19"W & rear of 7"H x 15"W, depth stays the same.

Your thoughts, opinions, ideas?

The answer is more complicated than that. Yes, keeping the volume of a given design the same is crucial, as is using the driver the box was designed for. However there are some considerations that also come into the equation. For instance if it is a cube, then the internal reflections all have the same path, and this can lead to a peak.
A cabinet with the driver close to the back wall is likely to cause trouble, as the short wave length reflections are likely to color the sound. In general though, you are correct, but as so often in life there are caveats.

As far as TLs, there are many more constraints. Driver position, length of pipe, pipe volume, rate of expansion, port area and type, weight and distribution of damping material have to be correct. All these are determined by the T/S parameters of the driver. In addition driver selection for TLs is more difficult as many are called as they say, but few are chosen.

I am a veteran of TL design so to speak. I have the great privilege to be the custodian of George Augspurger's model and design program. This is by far the best model, and in my view the only truly accurate one. You can download it for free on my website.

 

[Benni777]

Ty, TLS Guy. Certainly some considerations here. I'll have to check out your program. Again as for the change in parameters depth does not change only front, rear, top and bottom panels giving a bit of a skew for that trapezoidal look. As a reference I am building Danny Richie's A/V line of speakers. More specifically the A/V 3s and A/V 3. Although the TL is not fully certain as of yet. But I do currently own the center channel kit A/V-3s

 

[TLS Guy]

Ty, TLS Guy. Certainly some considerations here. I'll have to check out your program. Again as for the change in parameters depth does not change only front, rear, top and bottom panels giving a bit of a skew for that trapezoidal look. As a reference I am building Danny Richie's A/V line of speakers. More specifically the A/V 3s and A/V 3. Although the TL is not fully certain as of yet. But I do currently own the center channel kit A/V-3s

I can't seem to find much about those speakers, as that Richie chap says he is redesigning that A/V-3 series. Can you provide more information?

Specifically I would want to check the TL design, as most, if not all around, seem to have serious design errors. That is a pity as a properly designed TL is a truly wonderful speaker with very natural uncolored bass.

 

[Benni777]

I can't seem to find much about those speakers, as that Richie chap says he is redesigning that A/V-3 series. Can you provide more information?

Specifically I would want to check the TL design, as most, if not all around, seem to have serious design errors. That is a pity as a properly designed TL is a truly wonderful speaker with very natural uncolored bass.

I believe you want the blueprints ?

 

[Benni777]

I can't seem to find much about those speakers, as that Richie chap says he is redesigning that A/V-3 series. Can you provide more information?

Specifically I would want to check the TL design, as most, if not all around, seem to have serious design errors. That is a pity as a properly designed TL is a truly wonderful speaker with very natural uncolored bass.

Also to mention the redesigning on his website he's upgrading the tweeters to the x series tweeter, same woofer though. Not sure about the box design yet.

 

[TLS Guy]

I believe you want the blueprints ?

What are the woofers. The top woofer is in a sealed enclosure. The lower woofer is loaded. The design is what is known as an acoustic labyrinth, which is a TL variant.
One big problem I see, is that the loaded driver is right at the top of the line, and so will excite all of the odd harmonics, especially the third and fifth. So it will have high harmonic distortion. The driver should be located as close to the first node of the third harmonic as possible, which massively reduces harmonic distortion.

In honesty that is not a design I would do.

 

[Benni777]

I get ya, and honestly I was thinking of doing all sealed enclosures just for the ease of it. Not sure why the sealed ones are more than the TLs they use the same speakers. Perhaps the crossover changes idk. I am intrigued by doing a TL but idk. Maybe I'll stick to the sealed. Thanks again TLS Guy. Still want to check out your program though.

 

[TLS Guy]

I get ya, and honestly I was thinking of doing all sealed enclosures just for the ease of it. Not sure why the sealed ones are more than the TLs they use the same speakers. Perhaps the crossover changes idk. I am intrigued by doing a TL but idk. Maybe I'll stick to the sealed. Thanks again TLS Guy. Still want to check out your program though.

Before you do that, you had better model those drivers. A sealed enclosure has a much higher f3, usually about fs X 2. The TL with the same woofer if, designed properly and the driver is suitable for TL loading then the bass will be extended with a low Q and f3 will be close to fs.

I have to say that design makes no sense. A TL requires a Qts around 0.35 to 0.4 optimally, whereas sealed enclosures usually work better with a bit higher Qts drivers.

I suspect that crazy design was done to reduce size. Both drivers should have been loaded by the acoustic labyrinth. However using two drivers doubles Vas and therefore would have required twice the volume of air in the Labyrinth.

If you tell me what drivers they are, I can tell you if the drivers are suitable for TL loading and design you an optimal TL.

 

[Benni777]

Before you do that, you had better model those drivers. A sealed enclosure has a much higher f3, usually about fs X 2. The TL with the same woofer if, designed properly and the driver is suitable for TL loading then the bass will be extended with a low Q and f3 will be close to fs.

I have to say that design makes no sense. A TL requires a Qts around 0.35 to 0.4 optimally, whereas sealed enclosures usually work better with a bit higher Qts drivers.

I suspect that crazy design was done to reduce size. Both drivers should have been loaded by the acoustic labyrinth. However using two drivers doubles Vas and therefore would have required twice the volume of air in the Labyrinth.

If you tell me what drivers they are, I can tell you if the drivers are suitable for TL loading and design you an optimal TL.

M-130/16 woofer

This new woofer is a 16 ohm version of the extremely popular M-130, 5.25" woofer. It uses the same frame, curvilinear cone, dust cap, vented pole piece, and outer venting, but a larger motor structure was used and parameters designed in such a way as to offer good low end response in a ported...

www.gr-research.com

These are the woofers.

 

[Benni777]

FS 52.3 Hz
RE 12.9 ohms
Qms 2.329
Qts .447
Qes .554
Xmax 3.3 mm
L (1k) .55 mH
L (10k) .34 mH
Vas 15 Liters
Mms 7.825 grams
Cms 1.183 mm/newt
Bl 7.745 Tesla-M
SPL 87.7 db 1 watt/1meter
Area 95.05 sq cm

 

[Benni777]

As for the tweeter, he's changing them so they aren't online anymore

 

[TLS Guy]

As for the tweeter, he's changing them so they aren't online anymore

Well what ever you do you get a response that you would get from a good bookshelf.

Sealed gives you an f3 of around 100 Hz, TL loading lowers f3 to 60 Hz, and basically extends the response an octave lower. I estimated power handling at 75 watts, However you can see from the model it only handles 10 watts at 100 Hz in a sealed enclosure. The TL controls cone excursion much better, and you can see one of the huge advantages of a TL in controlling cone excursion. This is because both pipes and horns are highly efficient in converting air pressure to displacement. Pipe organs are the loudest instruments on the planet, and that's why.

In summary the drivers only good attribute is a really good looking smooth mid band response. So as a sealed driver it is pretty useless. It is not a good driver for ported application. A TL gives it a good enough bass response to be supplemented by a sub.

If you are going to use those drivers, I would do an MTM arrangement in a TL, that would get you good performance to 60 Hz, and it would be 15 db down at 30 Hz and 7.5 db down at 45 Hz.

Quite honestly though there are better projects to devote your time to.

 

[Benni777]

TLS Guy, Thanks for the above however let me clarify. I've bought the center channel MTM kit already. It contains two of the 5.25 woofers and one GRT3 tweeter and all of the crossover components plus the box design for a sealed box. He claims it is rated down to 85hz +-3db and can handle I believe 8-200 watts RMS ( I could be wrong on the wattage since reference is currently down).

So I am already in the works of building the center channel. Once I am done with the center channel I am going to proceed to the left/right channels which could be the same speakers as the center or perhaps the TL which seem to be the same speakers just different box and perhaps XO components IDK yet.

As of right now im invested since I own the center channel. I can only build, test and if I dont like sell and move on to another project. Hopefully I will be happy with them. But we shall see.

 

[TLS Guy]

TLS Guy, Thanks for the above however let me clarify. I've bought the center channel MTM kit already. It contains two of the 5.25 woofers and one GRT3 tweeter and all of the crossover components plus the box design for a sealed box. He claims it is rated down to 85hz +-3db and can handle I believe 8-200 watts RMS ( I could be wrong on the wattage since reference is currently down).

So I am already in the works of building the center channel. Once I am done with the center channel I am going to proceed to the left/right channels which could be the same speakers as the center or perhaps the TL which seem to be the same speakers just different box and perhaps XO components IDK yet.

As of right now im invested since I own the center channel. I can only build, test and if I dont like sell and move on to another project. Hopefully I will be happy with them. But we shall see.

He could be right, about 85 Hz, you did not tell me the box volume he used. If you tell me the box volume of that center, I will rerun the model. That will tell you exactly.

 

[Benni777]

He could be right, about 85 Hz, you did not tell me the box volume he used. If you tell me the box volume of that center, I will rerun the model. That will tell you exactly.

I'd have to get back to you on that but here is the box design

 

[Benni777]

Again id ike to change it a bit converting to a trapezoid.

 

[TLS Guy]

Again id ike to change it a bit converting to a trapezoid.

I modelled it with two drivers, and the dimensions of the box you sent me. So that gets f3 to 98.65 Hz. So not 85Hz. Now this is a model and not measured. However my experience with this program is that impedance is measured and modelled are in excellent agreement.

Now I did play with the box size, and those dimensions do give the lowest f3. If you increase the box size, f3 starts to rise fast. However the downside of that box is that it runs out of xmax with very little power at 110 Hz.

I will be honest, that is not a good design. Sealed boxes are highly inefficient in the bass. If you build that it really needs to crossed to the sub at around 120 Hz.

That design is just not a good practical design. If I had done it, I would keep very quiet about it!

Changing the shape of the cabinet to trapezoid will not matter.

Those drivers would be much better in a ported design. A 1.2 cu. ft cabinet, with a port 3" flared at both ends, and 3" in diameter and 6.2" long gives you an f3 of 48 Hz, and power handling of 55 watts at 80 Hz and common crossover point to subs.

That will be a much better speaker, more useful and practical. That Richie bloke needs a few lessons.

 

[Benni777]

Huh, interesting. Well, like I said I'm already invested so. I will be using a sub as well. But guess we'll see. My current 5.1 is a Energy RC micros, so these speakers should be better I would assume. But idk we'll see.

Thanks again for all your input.

 

[Benni777]

Originally I was going to buy emotivas speakers but found grresearch and wanted to try out diy.