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Old 21st October 2012, 05:05 AM   #21
Doug47 is offline Doug47  United States
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bjorno, I think I now understand the size and shape you are suggesting. It looks very doable (even with my limited woodworking ability).

I've been reading some on TL speaker design and one thing I run into is often (?) the box is stuffed with insulation (which is contrary to the "standard" reflex sub box design which just lines the walls with insulation). Other times, it seems not to be and then on some projects, they say to try out stuffing to see where the "sweet spot" is. So do I stuff the "tube" part, the part where the speakers are, both, or neither? Or do I experiment with stuffing to do the final tuning? I can use dowel rods or my original braces to keep the insulation from settling in the box.

Note that I will be going "dark" for the next week as I travel to Helsinki for a meeting with a bunch of European meteorologists. It doesn't mean I've abandoned the project, I am just not going to be able to update while sitting in my hotel room (or playing tourist around Finland).

Thank you very much for the added information.
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Old 30th October 2012, 04:20 AM   #22
Doug47 is offline Doug47  United States
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Quote:
Originally Posted by bjorno View Post
If you want to use more than one driver the the CSA:s S1,S2,S3,S4 and S5 must be enlarged correspondingly e.g.:

If 3 drivers then S1...S5 should be multiplied with 3 to get the correct areas bu the section lengths L12...L45 should alwauys remain the same.
I made the first step by duplicating your results. That's a good sign I at least am running Hornresp the right way.

Now it doesn't seem like either of the Hornresp outputs you show match the dimensions in the speaker diagram in the upper left hand corner. That's too bad as that design would really work well.

Since I will be driving each speaker with a separate channel of the amplifier, why can't I just increase the Sd parameter by a factor of 3, since all three of the speakers will be working the same way? I know that gives some odd results, but I can tune things to fix it (I think, I've not actually tried it yet).
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Old 30th October 2012, 04:25 AM   #23
Doug47 is offline Doug47  United States
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Quote:
Originally Posted by Cokewithlime View Post
You might want to have a look at the Exodus EX-Anarchy 6.5" driver it's definetly mechanically quieter and also IMHO more musical oriented(lower distortion) than the similar TB drivers.
Those look nice, but they are at least 2X the cost of the TB drivers. Not sure if I can swing that. Also the frequency response seems to be NOT as good on the low end (but I may be reading it incorrectly).
Quote:
Also while your at it you might want to really consider an alternative design, say something like building 2 of these proven, tested and measured LilMike designed Tapped Horns Two of then side by side should fit in the space you have available and may have a much higher WAF since they are much lower profile. As to the complexity of construction there are CNC flat packs available for that design - just a thought for you - btw you can use either the TB or the EX-Anarchy in that design.
There are almost 700 responses in that thread, and the pictures seem to be broken. So I don't know how big they are or where to get more information about getting the flat packs. Any suggestions would be helpful (and appreciated).
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Old 30th October 2012, 09:27 AM   #24
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by Doug47 View Post
I made the first step by duplicating your results. That's a good sign I at least am running Hornresp the right way.

Now it doesn't seem like either of the Hornresp outputs you show match the dimensions in the speaker diagram in the upper left hand corner. That's too bad as that design would really work well.

Since I will be driving each speaker with a separate channel of the amplifier, why can't I just increase the Sd parameter by a factor of 3, since all three of the speakers will be working the same way? I know that gives some odd results, but I can tune things to fix it (I think, I've not actually tried it yet).
Starting at Post#21

Quote:
I've been reading some on TL speaker design and one thing I run into is often (?) the box is stuffed with insulation (which is contrary to the "standard" reflex sub box design which just lines the walls with insulation).
Yes this is the main difference although both types belong to the same mechanical acoustical family= Degree of freedom = 2 but one relies on 'Half wave' and the other on 'Quarter-wave' to control the excursion at fb.

The Driver has a Qts of ~0.4 and a EBP (Energy Bandwidth Product) of~88 = fs/Qes indicating a suitability for a closed or a ported speaker. One could argue what the optimum use is.

A closed box designed for flattest response would be ~ 5.5L resulting in an f-3dB=~62 Hz or a larger box that returns a critical damped box with a Qtc of~0.5 needing a Volume of~22.6L but with an f-3dB of ~68 Hz.

A 4th order optimal BR using one element needs ~12.7L= Int. vol. less the port= tot. ~16.3L if tuned to ~34Hz which is also~f-3dB.

Scaling up x 3 times would imply a net 49 L box.

In post #20 I showed a design using 3 Drivers further practically optimized (-11.5L smaller) and a crude 'Paint' picture that only have a small typo error, that in reality, would minimally affect the resulting FR:

The internal dimension 32.5” should be 32.85”,i.e. L23 should be 18.64cm instead of 17.8 cm.

The Drivers are mounted in a row as close as possible to the S1 area but obviously cannot be kept centered at L12=64.8 cm if not horizontally mounted.

Practically, the driver Sd areas are distributed over a larger section length than shown in the simulation but still somewhere covers the stipulated L12 section length:
This is good enough and will return smoother off-band FR than the simulation predicts at the precise center location that HR uses.

The amount of needed stuffing must be simulated too but at a later time after an exact box Plan is posted by the DIY'r

b

Last edited by bjorno; 30th October 2012 at 09:30 AM.
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Old 30th October 2012, 03:44 PM   #25
Doug47 is offline Doug47  United States
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Quote:
Originally Posted by bjorno View Post
In post #20 I showed a design using 3 Drivers further practically optimized (-11.5L smaller) and a crude 'Paint' picture that only have a small typo error, that in reality, would minimally affect the resulting FR:

The internal dimension 32.5” should be 32.85”,i.e. L23 should be 18.64cm instead of 17.8 cm.

The Drivers are mounted in a row as close as possible to the S1 area but obviously cannot be kept centered at L12=64.8 cm if not horizontally mounted.

Practically, the driver Sd areas are distributed over a larger section length than shown in the simulation but still somewhere covers the stipulated L12 section length:
This is good enough and will return smoother off-band FR than the simulation predicts at the precise center location that HR uses.
Now I am starting to see, but I have a few questions that should help me understand things better (I want to "understand" what I am building, as much as possible). I hope these questions are clear enough (I may not know enough to ask good questions).

I just figured out where the 258.19 CSA comes from (forgot to subtract the width of the .75" board, duh).

1. You have L12 as 64.8 cm and L23 as 17.8 cm (or 18.64 cm in the corrected version). From what point are these measured? I see the "center" of speaker set about 26.7 cm (17.8 + 8.9) from the "bottom" of the first cavity in the diagram (the LEFT end of the schematic, or the S1 point) and 55.8 cm from the start of the second cavity (the L45).
2. I get different answers if I use "parabolic", "conic", etc., even though the change is diameter is a step function and not any of those curves. What fundamental concept am I missing? What does the "parabolic" refer to (since none of the walls are curved)?

Thanks for working with me on this. What I find interesting is how different Hornresp and WinISD suggestions are. Since both are trying to model the same concept (a box, a speaker, a port, the responses), they should converge at some point, maybe a cubic box?

Last edited by Doug47; 30th October 2012 at 03:47 PM.
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Old 31st October 2012, 03:27 PM   #26
Doug47 is offline Doug47  United States
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Quote:
Originally Posted by Doug47 View Post
1. You have L12 as 64.8 cm and L23 as 17.8 cm (or 18.64 cm in the corrected version). From what point are these measured? I see the "center" of speaker set about 26.7 cm (17.8 + 8.9) from the "bottom" of the first cavity in the diagram (the LEFT end of the schematic, or the S1 point) and 55.8 cm from the start of the second cavity (the L45).
Now I just thought of another interpretation of the situation. The measurements you used (64.8 & 18.6) are where the speakers SHOULD be. The diagram on the upper left is just an illustration of the general situation (speakers close together, a long secondary cavity that opens to the front, etc.). To implement the design, I need to put the speakers at the S2 position.

Now I do have one more question about the "position of the speakers". I would assume the "position" (or the S2 point) would be at the midpoint of the middle speaker. So in the diagram, the "position" of the speakers (S2) is about 26.7 cm. To build the modeled sub-woofer, I would need to move the speakers to 64.8 cm from the "bottom" of the first cavity. Is that a correct assumption?
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Old 31st October 2012, 06:35 PM   #27
Doug47 is offline Doug47  United States
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Quote:
Originally Posted by bjorno View Post
Practically, the driver Sd areas are distributed over a larger section length than shown in the simulation but still somewhere covers the stipulated L12 section length:
THIS part I understand.
Quote:
This is good enough and will return smoother off-band FR than the simulation predicts at the precise center location that HR uses.
Okay, this part I do NOT understand. The speakers (in the diagram) seem to be much lower in the first cavity than indicated by the HR output (much closer to S1 than 64 cm).
Obviously, I am missing something here.
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Old 31st October 2012, 06:37 PM   #28
mat3833 is offline mat3833  United States
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you have enough space to utilize a single 8" driver tuned fairly low. my current HT subs are Image Dynamics ID8v3's. here are the specs:
Re - 1.95 / 7.8 ohms (DC resistance Series/Parallel)
Fs - 24.7 hz (Resonant Freq)
Qes - .367 (Electrical "Q")
Qms - 3.572 (Mechanical "Q")
Qts - .332 (Total "Q")
Vas - 1.55 cu ft(44 liters) (Equivalent Volume)
Xmax - 15 mm (One way linear excursion)
Sd - 231 cm2 (Cone Area)
Spl - 85.6 dB Sensitivity o
Pwr - 150rms/300peak (Power Handling)

this is all info from ID direct. i never got the chance to run them at rated power in my home because the cooling fan went out in my HT amp about a week before i received them. but i tossed them on ~30W each in a 1.5ft^3 sealed enclosure for breakin and they are seriously impressive on low power. i had them in my car on 500W each and honestly, i dont think i could ask for more performance from 2 8" woofers at their price. they come in Dual 4 coils and dual 2 coils.(D4 coild can be 2 ohm or 8 ohm and D2 coild can be 4 ohm or 1 ohm final load)

i think with your power and space, an ID8 would serve you well, especially with its low Fs value. i can play a 20 hz tone on 30W and actually get things to move on the shelf above the subs, and thats in a sealed enclosure. if you would like i can model you a box with your space limits and post some screenshots of Winisd and torres for comparison.

Matt
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Old 31st October 2012, 10:06 PM   #29
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Quote:
Originally Posted by Doug47 View Post
Those look nice, but they are at least 2X the cost of the TB drivers. Not sure if I can swing that. Also the frequency response seems to be NOT as good on the low end (but I may be reading it incorrectly).There are almost 700 responses in that thread, and the pictures seem to be broken. So I don't know how big they are or where to get more information about getting the flat packs. Any suggestions would be helpful (and appreciated).
The EX-Anarchy drivers handle about 2x the power of what the equivalent TB drivers will, but either will work in the design linked below.

Here's a better link and a good look at the plans just scroll down on the linked page, they are actually quite small, which is why I suggested two of them for your space.

EricH at AVS is the one to contact in regards to flat packs for this design here is the direct link to the flat pack kit on his website

Last edited by Cokewithlime; 31st October 2012 at 10:13 PM.
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Old 1st November 2012, 12:04 AM   #30
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3 drivers? Limited space? 3 amp channels available?
Consider building 3 single-driver units. One can be the plinth for the vase, the others can hide beside other pieces of furniture around the room. You'll get much more even bass response.
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