Tranmission Line Subwoofer enclosure build - help needed

[forty5cal1911]

Modeling up a Tline subwoofer build using an Acoustic Elegance IB10AU-4 driver I have lying around. I have modeled it both in Hornresp and George Augspurger’s Transmission Line Analog software.

I want to thank @TLS Guy for hosting this excellent software!

I need a few pointers by anyone familiar with this software or Dr. Mark if you see this. This is basically an offset driver folded TL. Pipe length is 3 meters and driver location is at 1 meter. Pipe is 350 cm/sq linear throughout. I will include the parameters I have put into the enclosure in the software. I just need a sanity check as I'm not sure if I have modeled the throat area correctly and was unsure of what the stub length indicated. It's quite different than Hornresp with it's use of segment lengths.

Physical enclosure mock up:

Here is what I've got for modeling:

Thanks to anyone who can help me out here.

 

[TLS Guy]

Modeling up a Tline subwoofer build using an Acoustic Elegance IB10AU-4 driver I have lying around. I have modeled it both in Hornresp and George Augspurger’s Transmission Line Analog software.

I want to thank @TLS Guy for hosting this excellent software!

I need a few pointers by anyone familiar with this software or Dr. Mark if you see this. This is basically an offset driver folded TL. Pipe length is 3 meters and driver location is at 1 meter. Pipe is 350 cm/sq linear throughout. I will include the parameters I have put into the enclosure in the software. I just need a sanity check as I'm not sure if I have modeled the throat area correctly and was unsure of what the stub length indicated. It's quite different than Hornresp with it's use of segment lengths.

Physical enclosure mock up:
View attachment 58303

Here is what I've got for modeling:

View attachment 58304

View attachment 58305

Thanks to anyone who can help me out here.

What you have is an acoustic labyrinth. Making the baffle spacing identical is a bad mistake. You need to progressively narrow the spacing to get the effect of a taper and spread the range of support to the driver. One of the huge advantages of a TL is the range of support offered to the driver. Your design has negated that.

Labyrinths done properly can achieve excellent results. The Qts. of that driver is on the high side for TL, but not totally out of bounds. Also I do not advocate wool as the damping material. The cheaper and easier to work with Polyfill is better.

 

[forty5cal1911]

Thank you so much for your pointers.

I had spaced the baffles at an even 4.5" to get the 348 cm /sq cross sectional area. If I progressively space the last three at 4" , 3.5" and finally 3" on exit giving me a 232 cm/sq exit does that accomplish the taper adequately? This would make it a mass loaded TL due to the taper is that correct?

Changing the exit to 232 cm/sq appears to have positively affected the excessive excursion at low frequencies in the model.

As for the fill material I am fine using poly fill but had read (yeah I know.... gotta love the Internet!) that it was not effective in a TL and that wool was the proper material. Is the 8 grams per liter a good guideline and do I stuff every area of the pipe all the way into the last segment?

 

[TLS Guy]

Thank you so much for your pointers.

I had spaced the baffles at an even 4.5" to get the 348 cm /sq cross sectional area. If I progressively space the last three at 4" , 3.5" and finally 3" on exit giving me a 232 cm/sq exit does that accomplish the taper adequately? This would make it a mass loaded TL due to the taper is that correct?

Changing the exit to 232 cm/sq appears to have positively affected the excessive excursion at low frequencies in the model.

View attachment 58308

As for the fill material I am fine using poly fill but had read (yeah I know.... gotta love the Internet!) that it was not effective in a TL and that wool was the proper material. Is the 8 grams per liter a good guideline and do I stuff every area of the pipe all the way into the last segment?

When Joe D'Appolito investigated this in his paper, he found that Polyfill was better than wool. It also lasts better and is not prone to get invaded by pests. I strongly recommend against wool. It has to be hard to find long fiber wool anyway. There is Audiophoolery here, where the simple solution is never the best!

The damping weight calculation of that program is dead right. You should space it evenly, but not quite all the way to the end. I would leave the last compartment at the opening free of damping. I would use a 3 to 1 taper, with the widest at the closed end. This is called a reverse taper, which gives the best results.

If you get the Dayton Woofer Tester from parts express, you can check the damping. A properly damped TL should have just one peak of impedance like a sealed enclosure. If there are two peaks, then it is underdamped and will roll off at 24db per octave and not 12db per octave. If there is a small remnant of the second peak that is OK. Make sure the damping is even throughout, under no circumstances should there be any areas where the damping is compressed.

 

[TLS Guy]

When Joe D'Appolito investigated this in his paper, he found that Polyfill was better than wool. It also lasts better and is not prone to get invaded by pests. I strongly recommend against wool. It has to be hard to find long fiber wool anyway. There is Audiophoolery here, where the simple solution is never the best!

The damping weight calculation of that program is dead right. You should space it evenly, but not quite all the way to the end. I would leave the last compartment at the opening free of damping. I would use a 3 to 1 taper, with the widest at the closed end. This is called a reverse taper, which gives the best results.

If you get the Dayton Woofer Tester from parts express, you can check the damping. A properly damped TL should have just one peak of impedance like a sealed enclosure. If there are two peaks, then it is underdamped and will roll off at 24db per octave and not 12db per octave. If there is a small remnant of the second peak that is OK. Make sure the damping is even throughout, under no circumstances should there be any areas where the damping is compressed.

One other tip. You need to stop the damping material settling. If you use glue, then it hardens the Polyfill and it does not work as it should. I use netting over the Polyfill stapled with nylon mesh. The net they use to wrap Christmas trees works perfectly.

 

[forty5cal1911]

When Joe D'Appolito investigated this in his paper, he found that Polyfill was better than wool. It also lasts better and is not prone to get invaded by pests. I strongly recommend against wool. It has to be hard to find long fiber wool anyway. There is Audiophoolery here, where the simple solution is never the best!

The damping weight calculation of that program is dead right. You should space it evenly, but not quite all the way to the end. I would leave the last compartment at the opening free of damping. I would use a 3 to 1 taper, with the widest at the closed end. This is called a reverse taper, which gives the best results.

If you get the Dayton Woofer Tester from parts express, you can check the damping. A properly damped TL should have just one peak of impedance like a sealed enclosure. If there are two peaks, then it is underdamped and will roll off at 24db per octave and not 12db per octave. If there is a small remnant of the second peak that is OK. Make sure the damping is even throughout, under no circumstances should there be any areas where the damping is compressed.

Thank you Mark for this invaluable info! Especially the 3 to 1 taper ratio. Is there any good rule of thumb regarding how much larger than SD the closed end of the line should be for ideal performance?

I noticed when I was designing in Hornresp that I was seeing impedance plots with the signature bass reflex cabinet dual peak when I was doing some modeling. Of course I had not modeled any fill material. I have been needing to pick up a DATS unit for awhile now and this give me the perfect excuse.

Really, Thanks again for sharing your wealth of knowledge!

 

[TLS Guy]

Thank you Mark for this invaluable info! Especially the 3 to 1 taper ratio. Is there any good rule of thumb regarding how much larger than SD the closed end of the line should be for ideal performance?

I noticed when I was designing in Hornresp that I was seeing impedance plots with the signature bass reflex cabinet dual peak when I was doing some modeling. Of course I had not modeled any fill material. I have been needing to pick up a DATS unit for awhile now and this give me the perfect excuse.

Really, Thanks again for sharing your wealth of knowledge!

The program calculates the port area, and that is what it should be. The pipe volume is crucial, and is dependent on the Vas of the driver. This was George's great contribution in his paper of 2000, showing that pipe volume had a relationship to the Vas of the driver, as it does in a reflex ported enclosure. So if you know the taper is three to one, and you know the pipe length from the program, then you can work out the dimensions of the top and end of the pipe to get Vp (pipe volume) and then you can determine the overall dimensions. Pipe length should be calculated at the turns, by taking the center of the dimension to the boundaries. It is crucial you get pipe length and volume correct to have a successful design.

I will be interested to know the end result of this design.

 

[forty5cal1911]

Pipe length should be calculated at the turns, by taking the center of the dimension to the boundaries. It is crucial you get pipe length and volume correct to have a successful design.

I will be interested to know the end result of this design.

This is how I have calculated the pipe length (red line).

Do I need to be measuring all the way to the front and rear walls? I was thinking fluid path was what I would want to measure.

I will be very interested to see my results here as well as a properly engineered TL cabinet has such good transient response with very little ringing. If it is successful it will be almost wholly due to your assistance with the design.

I have some deer netting that is very similar we have used on our garden that should work pretty well to contain the polyfill.

 

[forty5cal1911]

So I have modified my design and stepped down the baffle spacing width after the driver to 4", 3.5", 2.5" and 1.5" on exit to give me the 3 to 1 ratio 116 cm/sq on exit. I have changed the taper profile in the software to special and corrected the linear taper to a stepped taper with the correct cross sectional area at each length specified.

My math came out to 2.83 cu ft or 80 L and the software has now calculated 78.83 L volume so I feel good with that as long as I'm performing the pipe length measurement correctly. The new calculations have not significantly altered the modeled response.

 

[TLS Guy]

So I have modified my design and stepped down the baffle spacing width after the driver to 4", 3.5", 2.5" and 1.5" on exit to give me the 3 to 1 ratio 116 cm/sq on exit. I have changed the taper profile in the software to special and corrected the linear taper to a stepped taper with the correct cross sectional area at each length specified.

View attachment 58330

My math came out to 2.83 cu ft or 80 L and the software has now calculated 78.83 L volume so I feel good with that as long as I'm performing the pipe length measurement correctly. The new calculations have not significantly altered the modeled response.

View attachment 58331

The way you have drawn it, is absolutely correct. It looks as if you are set to go. You will have to let is know how this project turns out.

 

[forty5cal1911]

The way you have drawn it, is absolutely correct. It looks as if you are set to go. You will have to let is know how this project turns out.

Thank you! I will update this thread as I'm going through the build. Hopefully my meager fabrication skills can execute this.

 

[TLS Guy]

Thank you! I will update this thread as I'm going through the build. Hopefully my meager fabrication skills can execute this.

As far as I know, you are the only member here to actually, use George's program and seek my advice on the build. I certainly hope your build is a success. You seem to have good design skills.

What you could do is find a a C & C cabinet shop and submit plans for each board and have them do the cutting and routing. Charges are usually very reasonable, and if you don't have good tools that would be worth it and cost effective. Then all you will need to put it together is glue and cabinet clamps. The mounting hardware for the driver. I did that with my in wall build. I turned up to the shop at 8:00 AM. By noon I was on my way home with the parts for my two right and left speakers, the center, the TL sub and four back boxes for the ceiling Atmos speakers in my AV room.

 

[forty5cal1911]

I've got to say Mark your studio is stunning! I really love the way you've got the chase room with proper conduit and room to access all the patching, interconnects and gear. WOW your attention to detail is impeccable. That is very impressive. Would love to hear your setup.

I was half messing around as I don't do a lot of cabinet fabrication but I have all the essentials. Table saw, mitre saw, jigsaw, planer, air tools brad nailer, stapler etc. Only thing I don't have is good router but will either borrow one or buy one as next up I will be building my floorstanding main cabinets. Will be a 3 way active setup with Peerless drivers mated to this sub.

We're going to be finishing out a bonus room in our upstairs about 900 sq ft. That will serve as my theater and listening room.

 

[TLS Guy]

I've got to say Mark your studio is stunning! I really love the way you've got the chase room with proper conduit and room to access all the patching, interconnects and gear. WOW your attention to detail is impeccable. That is very impressive. Would love to hear your setup.

I was half messing around as I don't do a lot of cabinet fabrication but I have all the essentials. Table saw, mitre saw, jigsaw, planer, air tools brad nailer, stapler etc. Only thing I don't have is good router but will either borrow one or buy one as next up I will be building my floorstanding main cabinets. Will be a 3 way active setup with Peerless drivers mated to this sub.

We're going to be finishing out a bonus room in our upstairs about 900 sq ft. That will serve as my theater and listening room.

Yes, you will need a router. If you have a table saw, a dado blade will help you. They really speed the job up, and then you only need the router to mount the drivers. I cut a larger circle as a guide for the router, and pin the template to the board.

 

[forty5cal1911]

I have a friend who is a cabinet builder and am going to enlist his help in building this enclosure. Not to mention he has commercial quality tools.

Here is the image of the final enclosure design. Front face driver baffle will be baltic birch and the rest 3/4" MDF.

And I've attached my sketchup model for anyone who is interested.

Hoping to get started in the next couple of weeks but with the holidays coming up we'll have to see.

Phil

 

[TLS Guy]

I have a friend who is a cabinet builder and am going to enlist his help in building this enclosure. Not to mention he has commercial quality tools.

Here is the image of the final enclosure design. Front face driver baffle will be baltic birch and the rest 3/4" MDF.

View attachment 58371

And I've attached my sketchup model for anyone who is interested.

Hoping to get started in the next couple of weeks but with the holidays coming up we'll have to see.

Phil

Let s know how it all turns out. I cold not open your file. I guess I don't have the correct voodoo loaded up.