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Discussion Starter · #1 ·
So I've got a pair of TD15X's, a pair of B&C DE500's, and a pair of QSC waveguides on the way all set to arrive next week. I'm not dead set on the XO but am thinking somewhere between 900hz and 1.2kHz. I'm using a DCX2496 for crossover so can tweak that quite a bit. I'm trying to design the enclosure now. I'm thinking of going ported even though my IB sub is good up to 120hz. I've tried to eye up how big of an enclosure I can put up with and I think 20" wide x 18" deep x 48" high looks pretty reasonable. I could stretch any of the dimensions a bit but don't want to stretch them all too much. That gives me about 225l (or 8cuft) to work with. Where I'm having trouble is juggling enclosure size, port air velocity, and port resonances. I found an old thread where John recommends 140l tuned to 27hz with a 3"x16" slot port 26" long. I modeled this up but found that that puts the first port resonance really low - well within the passband the TD15X will be playing in (in fact the 2nd, 3rd, and 4th resonances are probably in the passband with that setup too). I have some 4" PVC pipe in the garage so was looking at using that tuned to around 30-35hz. If I only use one port the 1st port resonance is just out of my passband but then the air velocity gets too high. If i move to dual 4" ports the air velocity is under control but then the port resonance is right back in my passband again! If I make the box bigger the port gets shorter and therefore resonance goes up but I can't go much bigger than this. Also if I just tune higher I end up with a big bump in the FR at tuning.


Any thoughts? Am I better off just sealing it? I just hate to waste the extra low end (and reduced THD on the low end) that ported would add for this build. The more I think about it the more I think I should just seal it up...


I should add I'll be powering with a 100W/ch Onkyo receiver for now but will likely be upgrading to a pair of pro amps when $ becomes available (so I've been modeling sending it 400W or so to see the "worst" case for chuffing).



Here's the T/S params:

TD15X- 8ohm

Fs 23.2 Hz

Qms 3.82

Qes 0.31

Qts 0.28

Vas 467 Liters

Cms 0.45 mm/N

Mms 105 grams

Sd 855 cm2

Rms 4.0 Kg/S

Bl 16.7 T/m

Re 5.6 ohms

Z 8 ohms

Le 0.3 mH

Pe (max) 500 Watts

Pe (transient) 1000 Watts

"no" 1.82 %

1WSpl 94.8 dB

Linear Xmax 14 mm (peak)

Mech Xsus 20 mm (peak)
 

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Discussion Starter · #2 ·
Another question (I'm in way over my head here but have been dreaming of a setup like this and decided to go for it...) what kind of considerations should I be making regarding the baffle layout? I have a 1 1/4" roundover bit but have no idea what would be ideal or even how to figure it out... Any help here would also be greatly appreciated. It's freezing rain here today so I may get some garage time in, hopefully someone out there can help me decide on something so I can get building



I may just build it 20x18x48 sealed and figure out the port later...
 

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That box is bigger than a lot of subs - that ought not to be at all necessary for use w/one.


You can cut port velocity a bunch when considering the XO.


For instance, if you tune the box to the XO freq and have a 2nd-order HP on the 15, air velocity id reduced 30%.


The lower you tune compared to the XO freq, the more velocity is reduced.


You don't get the full benefit of max power handling, but you're hardly likely to need it and you still get the benefit of improved low end response, and having Fb below XO improves the in-band phase response.
 

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From my own noodling with the AE TD 15X ( simulation only ) I would stick with around 4-4.75 cubes tuned to around 33 hz, even if you are going to cross them around 80 hz. ( single TD 15 in one box )
 

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Discussion Starter · #7 ·
I've not really set on an XO frequency yet. It will be active so I'll be able to play with it a bit. I'm going to start with 1.2k but will be playing with XO's down to 900hz.


Regarding the enclosure size it seems the smallest I can make the baffle is about 20"x32". With the +/-10 degree vertical window that would put things a bit low for floor-standing but would make putting them on a stand kinda' silly as the stand would be ~16"... I think I'm going to compromise and go with a 20"x40" baffle, 14" deep. With the double baffle that should give me close to the 5cuft I'm going for once the displacement of the driver, waveguide, and port is subtracted.
 

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Quote:
Originally Posted by lennon_68 /forum/post/17991972


I've searched and searched but cannot seem to locate the dimensions of the QSC waveguide. Does anyone have them handy so I can draw up the baffle layout? Hoping (unrealistically) to get started in these today.

14x10"
 

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In some ways your project is similar to mine. I did AE TD15Xs in 4.6cuft boxes with dual PR15-1400 passive radiators. This is similar to the "God of Thunder" box that was used in the old unity kit.


I plan to test out my custom made 24" quasi-OS waveguides (500hz LeCleach mouth rollback) crossed directly to the TD15Xs. Brandon's measurements confirm what JohnJ himself said, that these drivers have a first surround resonance at 500hz, which results in a dip in the FR. You can see this for yourself in Brandon's measurements.

here


This means you have to accept this aberration if you are crossing up at ~1khz. How troublesome is this really, I don't know. Scanspeak lovers accept a similar thing at 800hz all the time.


My waveguides will support at least down to 800hz, but going lower will be needed to be verified before doing. I intend to do some experimentation.


Just thought I'd say, that I am wandering down a similar path and share my thoughts thus far. My boxes are built but I haven't done measurements yet or testing them out.
 

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Discussion Starter · #11 ·

Quote:
Originally Posted by Monger /forum/post/17992305


14x10"

Thanks Nate! Say, when I was looking through threads of similar builds I saw you're doing something similar as well. I went looking for your thread but didn't find one. Do you not have a build thread yet or is it on a different forum maybe?

Quote:
Originally Posted by AudioJosh /forum/post/17992430


In some ways your project is similar to mine. I did AE TD15Xs in 4.6cuft boxes with dual PR15-1400 passive radiators. This is similar to the "God of Thunder" box that was used in the old unity kit.


I plan to test out my custom made 24" quasi-OS waveguides (500hz LeCleach mouth rollback) crossed directly to the TD15Xs. Brandon's measurements confirm what JohnJ himself said, that these drivers have a first surround resonance at 500hz, which results in a dip in the FR. You can see this for yourself in Brandon's measurements.

here


This means you have to accept this aberration if you are crossing up at ~1khz. How troublesome is this really, I don't know. Scanspeak lovers accept a similar thing at 800hz all the time.


My waveguides will support at least down to 800hz, but going lower will be needed to be verified before doing. I intend to do some experimentation.


Just thought I'd say, that I am wandering down a similar path and share my thoughts thus far. My boxes are built but I haven't done measurements yet or testing them out.

Thanks for the input, do you have a build thread somewhere I could follow/read through? I have seen the measurements and will try treating the FR with notch filters to see how I prefer the sound.
 

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"I've not really set on an XO frequency yet. It will be active so I'll be able to play with it a bit. I'm going to start with 1.2k but will be playing with XO's down to 900hz."


I meant XO to sub.


"I would stick with around 4-4.75 cubes tuned to around 33 hz, even if you are going to cross them around 80 hz. ( single TD 15 in one box )"


Why? That's likely (at least it does w/a B&C 15TBX100, which I have parameters for) to give *less* bass in the passband than a properly sized sealed box.
 

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Discussion Starter · #13 ·

Quote:
Originally Posted by noah katz /forum/post/17993157


I meant XO to sub.


"I would stick with around 4-4.75 cubes tuned to around 33 hz, even if you are going to cross them around 80 hz. ( single TD 15 in one box )"


Why? That's likely (at least it does w/a B&C 15TBX100, which I have parameters for) to give *less* bass in the passband than a properly sized sealed box.

Oh, right. I'm currently running my IB up to 120hz (it's an "outie" so it works fine) but I'll be crossing at more like 80 or 60 with these, depending on how it sounds once I've got them up and running. In 5cuft tuned to 30hz it's flat down to 80hz, -1dB @ 50hz, and -3dB @ 40hz. Sealed in 5cuft it's flat to 200hz, -1dB @ 100hz, and -3dB @ 60hz. It probably won't be much of a difference in the passband but excursion is matched with more output on the ported down to 50hz so why not try the ported version.
 

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Quote:
Originally Posted by noah katz /forum/post/17993157


Why? That's likely (at least it does w/a B&C 15TBX100, which I have parameters for) to give *less* bass in the passband than a properly sized sealed box.

I guess it depends on your needs. This is the box without any room gain, both modeled with 50F temp rise, and a drive level of 50 watts.

http://www.avsforum.com/avs-vb/attac...1&d=1264365620


Same boxes, but with a highpass at 80 hz.




Either cabinet will work well, IMO. If you were doing 2 channel audio without subs, I would definately build the vented version.


With the same footprint, building a 3 cubic foot sealed box might require a riser, whereas the vented version would most likely not. ( to put the compression driver up around ear level )

 

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OK, I guess the TD15 has quite different parameters than the B&C.


"building a 3 cubic foot sealed box might require a riser, whereas the vented version would most likely not."


The volume can be reduced by reducing the depth instead of the height.
 

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Yeah, if you don't mind the big boxes, build them ported so they can run without subs.


Since you're using a DCX, getting a good blend with the sub is easy. EQ the speaker to a 2nd order, Q=.7 roll-off at the receiver's XO frequency and it will be perfect. The receiver does 4th order on the sub and 2nd order on the speaker. Add in the speaker's 2nd order roll-off and you're stylin' with 4th order acoustic on both the speaker and the sub.
 

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You had asked if I had a build thread. I do but not on this forum.

http://www.audiocircle.com/index.php?topic=69181.0


Hope this is kosher to link to another forum.


My project takes zigs and zags with my thinking. Its just my MO. But due to 1) a DEQX and 2) lots of different drivers and waveguides at my disposal, I can experiment.


When Jeffrey Jackson announced his elevenhorn.com business, I took the opportunity to have some custom made waveguides done in a large size. The CD I'll be using for those is the 18Sound ND-1040As.


I still plan to experiment with the abbey clone looking tops.
 

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Discussion Starter · #18 ·

Quote:
Originally Posted by AudioJosh /forum/post/17995309


You had asked if I had a build thread. I do but not on this forum.

http://www.audiocircle.com/index.php?topic=69181.0


Hope this is kosher to link to another forum.


My project takes zigs and zags with my thinking. Its just my MO. But due to 1) a DEQX and 2) lots of different drivers and waveguides at my disposal, I can experiment.


When Jeffrey Jackson announced his elevenhorn.com business, I took the opportunity to have some custom made waveguides done in a large size. The CD I'll be using for those is the 18Sound ND-1040As.


I still plan to experiment with the abbey clone looking tops.

Thanks for the link. Funny, I was just reading your thread yesterday, came up when I was searching for similar builds
I'll have to keep my eye on it and see where you end up.


Quote:
Originally Posted by catapult /forum/post/17995229


Yeah, if you don't mind the big boxes, build them ported so they can run without subs.


Since you're using a DCX, getting a good blend with the sub is easy. EQ the speaker to a 2nd order, Q=.7 roll-off at the receiver's XO frequency and it will be perfect. The receiver does 4th order on the sub and 2nd order on the speaker. Add in the speaker's 2nd order roll-off and you're stylin' with 4th order acoustic on both the speaker and the sub.

Yeah, that's what I'm thinking too. Since it will just be the front two (I'll be trying a phantom center for now) I'll be using the DCX to manage the XO to the sub as well which should make integration a snap.
 

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Quote:
Originally Posted by lennon_68 /forum/post/17988276


Thanks Noah. I think I'm just going to go back to 140L tuned to 30hz with one 4" port. I'm reading through Findbuddha's thread now as it looks like he's already asked (and received answers to) nearly all of the questions I have

I bought my 15X's with the intention of using them sealed in about 80L net/driver (2 drivers/ch, Q=0.7) knowing that I'd have enough displacement capacity to add an LT or other EQ to get me to 35-40Hz, enough for music, and use subs for movies below this.


When I drew up the boxes I found I had about 140L net/driver. Later I was looking at 6th order ported alignments, and for the 15X this is 163L net, for a tuning of 24Hz. All you need to add is a 24Hz Q=2 LP filter.


I might stretch my boxes a bit to get the extra 20L + ports, so I can potentially have 3 LF tuning options.


My 15X will only be run to 350Hz.
 
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