SEOS 18, TD15M, BA750 build

SEOS 18, AE TD15M, Denovo BA-750, active crossover, distributed subs --(2) group buy Anarchy 6" folded horns, (1) 12" sealed.


First I'm going to build boxes for my pair of TD15M's. I like the idea of having bass bins with the CD/waveguide assemblies either having separate simple boxes or hardwood brackets to hold them in place. This way I'll have flexibility in case I want to try other waveguides. I'd like to have the F3 fairly low so I'll need to have a vented box and apply equalization. Presently, I'm using WinISD beta. I found winISD Pro full of bugs.
I entered the TD15M parameters and specified a tuning frequency of 35Hz. Since the Fs is 34.7, the drivers should be able to handle 35Hz. However, the graph said that it'll be down 7db @35Hz. Is this too much to equalize? I decided to model 40hz. I do like the 35Hz because it would make the woofers closer to subs therefore work well with my subs.
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Here's the graph for four different boxes.



The F3 65Hz box has a 5db bump around 80Hz. The 35hz box is down 7db at tuning freq.The sealed and vented (40Hz) boxes seem to display smoother responses so are they should be more optimum. Am I reading this right? I'm a newbie when it comes to speaker design and this is the first time I've worked with winISD or used active equalization. How far can I push the woofer to change the response? I'm using the basic program, not the beta pro version which I found buggy.



Could I push a sealed box design lower (~40hz) with equalization and without affecting sound quality? It would be ideal if I could use a sealed box thereby avoiding huge and expensive bass bins.



Here are four boxes I modeled.


yellow-- sealed box: W: 18.00 in., H 19.36in., D 12.00in 2.42cu. ft. F3~75Hz
blue--vented box: W 18.00 H 30.00in, D 19.20in 6.00cu. ft. F3 65Hz (1) 6"vent
green--vented box: W 18.00 H 30.00 D 19.20 6.00cu. ft. F3 40Hz (2) 4"vents
orange--vented box W 18.00 H 30.00 D 19.20 6.00cu. ft. F3 35Hz (2) 4" vents

From the look of the numbers I think I'll go with the 40hz box. Of course, I'd prefer a smaller box but going sealed would sacrifice much of the capability of the TD15M.


In conclusion, the 40hz vented box is the best compromise. Unless I get feedback that I'm all wet or a better sealed option is possible ....40hz vented is it for me unless I change my mind again. : You can drive yourself batty modeling all the possibilities.
This will be for 95% music 5% HT.

 

[font=verdana, arial, helvetica, sans-serif]This will not be a one piece speaker but a bass bin with the WG mounted on top. The woof will be as close as possible to the top of the bin to keep center to center distance at a minimum. I'd like the CD to be about 37" off the floor at listening height. I have to account for 1/2 the WG height (~4") plus the thickness of the top and bottom of the box. Also the bins will probably be mounted on spikes...~1". So let's say 2" for thicknesses, + 4" WG + 1" spikes = 7". 30" - 7" = 30" optimum height for inner dimensions for box. No doubt a 6 cu ft box with driver will be pushing 100lbs.[/font]
[font=verdana, arial, helvetica, sans-serif]The model specifies (2) 4" vents. I'm not sure where to place them. I know that Duke at AudioKinesis deploys 2 vents asymmetrically on the backside, one high and one low which keeps the air load on the back of the woofer more symmetrical. [/font][SIZE=78%]http://www.audiocircle.com/index.php?topic=94063.0[/SIZE]
...Roy

 

Hi Steve,


I'll have to check the Linkwitz transform out although it might be getting too much into deep weeds for me. It sure would be nice to have a small box though. I'm going to run some more models with different box sizes to see if I can find a smaller vented box that will work.


...Roy

 

Here's an interesting post by John, the owner of AE, relating to the TD15M.


In terms of output, a single TD15M in 6cubic foot tuned to 32-40hz will do well. In most cases for music you'll want to get down close to 30hz to cover the low B on bass guitar and low A on piano. The 40hz tune gives an F3 about 40hz, while the 32hz tune costs some efficiency but gives more extension. With the dsp unit you can then EQ this response back up if necessary. That would be the way I would go ideally. You'll still be capable of about 117dB at 40hz with 200W input. In terms of output, a single TD15M in 6cubic foot tuned to 32-40hz will do well. In most cases for music you'll want to get down close to 30hz to cover the low B on bass guitar and low A on piano. The 40hz tune gives an F3 about 40hz, while the 32hz tune costs some efficiency but gives more extension. With the dsp unit you can then EQ this response back up if necessary. That would be the way I would go ideally. You'll still be capable of about 117dB at 40hz with 200W input.

 

Here's the post. I'm having a little trouble with pastes. ???


In terms of output, a single TD15M in 6cubic foot tuned to 32-40hz will do well. In most cases for music you'll want to get down close to 30hz to cover the low B on bass guitar and low A on piano. The 40hz tune gives an F3 about 40hz, while the 32hz tune costs some efficiency but gives more extension. With the dsp unit you can then EQ this response back up if necessary. That would be the way I would go ideally. You'll still be capable of about 117dB at 40hz with 200W input.

 

Thanks for running those numbers. 19" for width is OK. It's surprising that you can actually compute the amount and placement of the stuffing. I'm still vacillating over the size of box and giving sealed another look. Since I'll be using the minDSP, equalization will be simplified whereas with a passive crossover trial and error can be expensive and time consuming especially for an amateur like me.


Here's an interesting review of a very high end speaker that uses the TD12M in a sealed box.[SIZE=78%]http://www.6moons.com/audioreviews/ariescerat/1.html[/SIZE]


" Key is that sealed bass—with a driver appropriate for such loading—shows up how some presumed room issues from ported bass systems are actually time-smear problems. Those 'magically' vanish when a sealed box of similar size hunkers down in the same spot which ought to cause identical room loading conditions but does not. That's not an asset to underestimate when one gets to the fundamental choice of whether the next speaker acquisition should look for sealed or ported bass"