# How much effect might sealed cabinet volume have on subwoofer upper-bass response?



## Grinder (Dec 18, 2016)

I’ll receive a brand-new pair of Dayton HF 15s tomorrow, and I’m not sure which of the following two sealed cabinet volumes might best suit my 2.2 home stereo application (i.e. to pick up where a pair of 100 Hz folded bass horns leave off, which begin to roll off ~100 Hz).

Parts Express recommends 2.88 ft.^3 sealed, for an F3 of 37 Hz.

…however, modeling this driver in WinISD at 2.88 ft.^3, yields a .815 Qtc, a 34 Hz F3, and a slight hump from 55 Hz to 220 Hz (with a 0.25 dB peak at 80 Hz), with roll off beginning at 55 Hz, and an F10 of 21.5 Hz.

…whereas 4.62 ft.^3 yields a .707 Qtc, a 33 Hz F3, and a flat response, with roll off beginning at 110 Hz, and an F10 of 19 Hz.

For obvious reasons, it would be easier to build the smaller cabinet. However, I have enough room for the larger cabinet (though not much more than that). So... 

*The question is, if it might make any noticeable difference, which of these two cabinet volumes might best meet the roll off of my bass horns; and why?
*


For reference:

While it is primarily used for HT, what matters most to me is SQ, while listening to literally ALL kinds of music.

The bass horns currently receive a line-straight/flat full-range signal (no EQ or HPF), with a Paradigm PS-1200 (4th order bandpass powered sub) picking up where the horns leave off. 

I don't like the results of running the receiver’s pre-outs through the Paradigm’s 50 – 150 Hz adjustable LPF; as it makes the bass horns sound even thinner; and the Paradigm itself generally sounds better (less peaky, muddy and boomy), the lower the LPF setting (which is, of course, far from ideal). Despite all that, it does a surprisingly decent job of keeping up with the horns (at virtually any level I can handle). 

However, I’d like a bit more depth, a lot more punch, and a whole other level of musicality, precision, definition, and transient response; to which I think the HFs are well suited; though I’m not nearly so sure how well they’ll blend with the horns (i.e. how far up they’ll comfortably reach, to hopefully meet the horns where they fall off).


The HFs will be powered by a Crown XLS 1502; and, if necessary (and in all likelihood), via a miniDSP 2x4 (for PEQ ...and LPF, in place of the XLS LPF).

...in which case, I could run the receiver's pre-outs through the remaining two channels of the miniDSP (to HPF the horns ...but likely not, due to highly efficient horns and relatively noisy miniDSP).


The horns (two each):

JBL Professional Series 2402H ultra-high frequency transducers (tweeters).
JBL Professional Series 2440 compression drivers (midrange horns).
JBL Professional Series 2309 horns (midrange horns). 
JBL Professional Series 2390 acoustic lenses.
Eminence EM-54-15-H18 15” pro woofers (100 Hz folded horns).


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## Justin Zazzi (May 28, 2012)

If you want to try and get a passive solution for the Dayton woofers that have a low-pass response to match the high-pass response of your folded horns, you'll need some massive inductors in a passive crossover, or an enclosure that has a natural low-pass filter such as a bandpass box, or a combination of the two. A bandpass box with that wide of a bandwidth would not have a very high sensitivity which might be a problem matching the loudness of your horns, and the inductors of a passive crossover would be huge and expensive.

You do have a MiniDSP and a separate amplifier though, so you can use whatever enclosure you want and get any low-pass frequency response you like without changing anything relating to the folded horns.

You can build a bigger box with a lower Qtc like 0.707. Or you can build a smaller box with a higher Qtc then use the MiniDSP to add a set of filters (like a Linkwitz Transform) to change the Qtc and frequency response to something more suitable. You'll need more power in a smaller box since the sensitivity will go down a little, but you get a smaller box which is cool and amplifier power is generally cheap anyways (seems like you have plenty anyhow).

Does that help?


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## Grinder (Dec 18, 2016)

Justin Zazzi said:


> If you want to try and get a passive solution for the Dayton woofers that have a low-pass response to match the high-pass response of your folded horns, you'll need some massive inductors in a passive crossover, or an enclosure that has a natural low-pass filter such as a bandpass box, or a combination of the two. A bandpass box with that wide of a bandwidth would not have a very high sensitivity which might be a problem matching the loudness of your horns, and the inductors of a passive crossover would be huge and expensive.
> 
> You do have a MiniDSP and a separate amplifier though, so you can use whatever enclosure you want and get any low-pass frequency response you like without changing anything relating to the folded horns.
> 
> ...


I think so. It sounds like I'll be better off with the larger box. 

I guess the heart of my question is, how well suited HF 15s might be, in terms of their inherent ability (or lack thereof) to meet my frequency response needs?

...and to the extent that they might be well suited, which of the two cabinet volumes would more readily meet the roll off of my horns (without DSP), while bearing in mind that I will almost certainly be using the miniDSP to make up for any shortcomings of the HFs in-room response; while more than likely running the horns full range, without HPF or PEQ (and bearing in mind that passive crossovers and bandpass enclosures are not an option)?


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## Grinder (Dec 18, 2016)

...The thing is, I'm confused by PE's recommended 2.88 cubes being so far from .707 Qtc; and I'm worried that my WinISD results might be flawed (for all I know, 2.88 cubes might actually be .707 Qtc - as suggested by a PE staff member in their HF 15 Product Q&A).

Also, a friend has led me to believe that the 2.88 cubes will provide better response up high (to better meet that of my horns) than the larger enclosure, but I'm just not seeing how the response in that area would be effected very much by this difference in cabinet volume.

If the WinISD modeling results I'm getting from these two volumes is correct, then it seems to me that my best bet would be the larger .707 Qtc cabinet.

But perhaps they're not correct; or perhaps it just doesn't matter much either way (and I'm overthinking this)...


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## Justin Zazzi (May 28, 2012)

Enclosures change the behavior near and below resonance. As you have seen, "near" resonance can also mean above resonance if you are introducing a peak with a higher Qtc. Enclosures generally don't modify anything above resonance, so your question is perhaps not chasing the right problem.

It seems like the behavior of your bass horns are set and you don't want to modify them. It seems like the woofer you chose for the subs is set (dayton). It seems like the enclosure type you chose is set (sealed). The last two things you can change are the enclosure size and the signal processing. I tried in my earlier to post to summarize the choices you have with enclosure size and signal processing. There are many combinations that will get what you want.

In this case, your enclosure and woofer choice do not have a low-pass frequency response in the range you're looking for so there is no "ideal" choice in enclosure size because you won't get the results you want without modifying the signal with a processor like the MiniDSP or a massive passive crossover that will be expensive.

If you went for something like a bandpass box or if you used a woofer with an absurdly high inductance from a crazy voice coil (like 8 layers or more) then you could try to optimize the enclosure. But using the woofer you have and a sealed box, you cannot.

Also remember when it comes time to place these in a room, the distances to the side and rear walls will have an incredible effect too and any small choices you make in enclosure size will be meaningless in comparison.

I would build the smaller box, move it around in the room a little bit for gross tuning, then fine tune it with active processing in the MiniDSP.


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## Grinder (Dec 18, 2016)

Justin Zazzi said:


> Enclosures change the behavior near and below resonance. As you have seen, "near" resonance can also mean above resonance if you are introducing a peak with a higher Qtc. Enclosures generally don't modify anything above resonance, so your question is perhaps not chasing the right problem.
> 
> It seems like the behavior of your bass horns are set and you don't want to modify them. It seems like the woofer you chose for the subs is set (dayton). It seems like the enclosure type you chose is set (sealed). The last two things you can change are the enclosure size and the signal processing. I tried in my earlier to post to summarize the choices you have with enclosure size and signal processing. There are many combinations that will get what you want.
> 
> ...


I'm afraid I don't understand much of what you're saying here. Are you saying that, on the one hand the HF 15 is not well suited to my application (given my chosen restraints); but on the other hand, they should fill the need just fine, given adequate processing?


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## Grinder (Dec 18, 2016)

Justin Zazzi said:


> Enclosures change the behavior near and below resonance. As you have seen, "near" resonance can also mean above resonance if you are introducing a peak with a higher Qtc. Enclosures generally don't modify anything above resonance, so your question is perhaps not chasing the right problem.
> 
> It seems like the behavior of your bass horns are set and you don't want to modify them. It seems like the woofer you chose for the subs is set (dayton). It seems like the enclosure type you chose is set (sealed). The last two things you can change are the enclosure size and the signal processing. I tried in my earlier to post to summarize the choices you have with enclosure size and signal processing. There are many combinations that will get what you want.
> 
> ...


Understood. Thank you.

While the smaller box would be slightly more convenient and easier to build, would there also be an advantage (as my friend suggested) in terms of response?


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## Justin Zazzi (May 28, 2012)

Grinder said:


> I'm afraid I don't understand much of what you're saying here. Are you saying that, on the one hand the HF 15 is not well suited to my application (given my chosen restraints); but on the other hand, they should fill the need just fine, given adequate processing?


Esentially, yes.

If you look at the frequency response graph from the datasheet (linked here) you will see a flat response from about 40hz through 1khz. As I understand it, you want the frequency response of the subwoofer you're going to build to have a low-pass so that the frequencies above around 100hz will fall off in a manner that will compliment the bass horns you already have (which play down to about 100hz). This is the big assumption I'm making in understanding your request, and it might be wrong, so please correct it.

Assuming that to be the case, any size sealed enclosure will not give you a rolloff of frequency response above 100hz because to answer your original question, _the size of a subwoofer enclosure does not effect the higher frequencies_. So the size of a subwoofer enclosure doesn't matter in terms of mating well with your bass horns unless you make it waaaaay too small with a high Qtc, which you won't. The enclosure does change the low frequency response, the power required to get the lower frequencies, and how convenient it is to have a large or a small box. These can also be changed with the amount of amplifier power you have and the processing available, which it sounds like you have plenty of both.

So if you make a "smaller" box that is convenient with a Qtc less than 1.0 such as 2.88 cuft, place it somewhere in the room where it behaves reasonably well, recover the lowest frequencies by adding more amplifier power and a Linkwitz Transform in the DSP, and tune the blending between the subs and the bass horns with DSP, you can have the best of everything.

I hope that makes more sense.


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## Grinder (Dec 18, 2016)

Justin Zazzi said:


> Esentially, yes.
> 
> If you look at the frequency response graph from the datasheet (linked here) you will see a flat response from about 40hz through 1khz. As I understand it, you want the frequency response of the subwoofer you're going to build to have a low-pass so that the frequencies above around 100hz will fall off in a manner that will compliment the bass horns you already have (which play down to about 100hz). This is the big assumption I'm making in understanding your request, and it might be wrong, so please correct it.
> 
> ...


That makes sense, and is exactly what I needed to know. Thank you!


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## SPLEclipse (Aug 17, 2012)

Just popped in to agree with Justin. Above the range where you're using resonance to modify the response it doesn't matter what kind of enclosure you have as long as the driver remains a direct radiator. Modal issues will be your biggest roadblock so measuring and moving it around might be necessary. You can also do the "bass crawl" by putting the sub at your listening position and playing music while crawling around on the floor and listening for the best resulting location.

edit: to add something, it might be possible to handle the lpf acoustically by pointing the sub into a corner to create a quasi bandpass effect. It's worth a try.


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## Grinder (Dec 18, 2016)

SPLEclipse said:


> Just popped in to agree with Justin. Above the range where you're using resonance to modify the response it doesn't matter what kind of enclosure you have as long as the driver remains a direct radiator. Modal issues will be your biggest roadblock so measuring and moving it around might be necessary. You can also do the "bass crawl" by putting the sub at your listening position and playing music while crawling around on the floor and listening for the best resulting location.
> 
> edit: to add something, it might be possible to handle the lpf acoustically by pointing the sub into a corner to create a quasi bandpass effect. It's worth a try.


Thank you.

Unfortunately, the location of these subs is yet another constraint. The only viable option as I see it, is to place one forward-facing, direct radiating sub cabinet atop each horn cabinet. Here's a picture of what I'm working with: http://www.diymobileaudio.com/forum/attachment.php?attachmentid=215922&d=1523162507

Alternatively, I suppose I could locate these sub cabinets immediately beneath each horn cabinet; however, while their 36" overall height presently places the top horns' horizontal center a couple/few inches lower than listening height, 46.5" (36" + 16.5" sub cabinet height - 6" = center of top horns) would place the top horns at least several inches higher than listening height. 

Also, for better or worse, I'm operating on the premise that these subs (like the Paradigm they will replace) won't sound as good (for my high LPF purposes) on the floor as they would atop the horns. 

...although, one of the reasons I've been attracted to the larger (4+ cubes - actually 4.5 gross) cabinet, is that it happens to be the product of 25" W (horn cabinet width) x 24" D (horn cabinet depth) x 16.5 H (minimum sub cabinet height); which would be the minimum dimensions required for the sub cabinets to be located beneath the horns if necessary (a form factor that might arguably look best atop the horns as well ...compared to the smaller 2.88 cube cabinets, whose depth would be shortened to ~16" ...placing the subs 16" closer to the rear wall - which would seem to be contraindicated for my high LPF purposes - lest there be an odd 16" + gap between the rear wall and the rear of the sub cabinets ...which, I suppose, might not look so odd at all ...no more than horn-top subs, anyway LOL).

In any case, it seems to me that these two HF 15s (+ miniDSP) ought to be a vast improvement over the one Paradigm sub ...in looks (debatable, I suppose), overall SQ potential, and potential suitability to this application.

Sorry about the TMI and rambling.

Thanks again, guys!

I will be sure to follow up with pictures and impressions.


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## Jeffdachefz (Sep 14, 2016)

best solution is none of the above if you actually have plenty of space.

A properly designed 1/4 wave transmission line will give you much more loud usable bandwidth than sealed(which rolls off like a mother, literally no wear near flat IMO.) Transient response and tightness feels a lot faster, punchier and accurate especially when it comes to fast double bass pedals in metal. Of course the output capability will blow your socks off as well needing very little power to get loud. I wouldnt be surprised if you hit down to 10hz with authority in a properly designed T line box for the dayton considering it's low FS. Upper bass response is every bit as good as sealed if not better in almost all cases of very low tuned T lines i've done and seen.

You'll have people argue that sealed can reach deeper but its a load of horse sh*t because it does reach it however its so little output its utterly useless well before you even hit the teens.


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## SkizeR (Apr 19, 2011)

Jeffdachefz said:


> Transient response and tightness feels a lot faster, punchier and accurate especially when it comes to fast double bass pedals in metal.


Loudspeakers are minimum phase devices, so transient response is directly related to frequency response.

Sent from my SM-G950U1 using Tapatalk


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## Grinder (Dec 18, 2016)

Jeffdachefz said:


> best solution is none of the above if you actually have plenty of space.
> 
> A properly designed 1/4 wave transmission line will give you much more loud usable bandwidth than sealed(which rolls off like a mother, literally no wear near flat IMO.) Transient response and tightness feels a lot faster, punchier and accurate especially when it comes to fast double bass pedals in metal. Of course the output capability will blow your socks off as well needing very little power to get loud. I wouldnt be surprised if you hit down to 10hz with authority in a properly designed T line box for the dayton considering it's low FS. Upper bass response is every bit as good as sealed if not better in almost all cases of very low tuned T lines i've done and seen.
> 
> You'll have people argue that sealed can reach deeper but its a load of horse sh*t because it does reach it however its so little output its utterly useless well before you even hit the teens.


Wouldn’t we all love to have 15” T-line subs!

While I suppose there actually would be enough space, presuming each cabinet would be no larger than 25" W x 24" D x 48" H; when placed atop the horns (which would be their only plausible location), they’d be seven feet tall ...or just two inches from the ceiling.

But hey, that might be A-Okay, and a quite reasonable compromise, given the comparative sonic merits of the design (of which I’m fairly well aware).

However, despite the nature of this thread, I suppose it might not be sufficiently clear that I’m not yet remotely qualified to properly design a 1/4 wave transmission line. 

Unfortunately, another constraint is that I lack a proper workshop and tooling (no table saw – only a Skilsaw, jigsaw, drill, and a few clamps; which can be a real PITA, but works just fine for simple cabinets).

Fortunately, I don’t need to get very loud. As stated above, the Paradigm sub is loud enough. I seek vastly improved SQ, and noticeably improved LFE (and with the miniDSP and XLS 1502 power, I’m confident that the sealed HFs will be plenty loud enough, and provide that extra bit of LFE. While the Paradigm gets down to ~30 Hz, and 10 Hz would be fantastic, I’ll be happy to get mid-to-low 20s with a bit of authority at modest listening levels).


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## Grinder (Dec 18, 2016)

SkizeR said:


> Loudspeakers are minimum phase devices, so transient response is directly related to frequency response.
> 
> Sent from my SM-G950U1 using Tapatalk


^^^^^ It's all Greek to me.




This helps a bit (but...):

(taken from http://www.diymobileaudio.com/forum...oudspeaker-impulse-response-optimization.html )


DanWiggins said:


> For a loudspeaker driver (a minimum phase device), impulse response, frequency response, and phase response are all inter-related. Optimize one, and you have optimized the others. You would need to use non-causal processing to decouple these.
> 
> Get the frequency response flat, and the impulse will be optimized.





Andy Wehmeyer said:


> DING DING DING...we have a winner. This IS the Fourier Transform. However...be careful--this applies to a minimum phase device only. that means one driver and no other radiating surfaces. A loudspeaker in a room isn't minimum phase. A loudspeaker with an additional tweeter isn't minimum phase either. Focusing on the impulse response at the expense of other aspects is a little like serving great wine with a bowl of microwave popcorn.
> 
> However, one really has to screw up a crossover and enclosure design to have an impulse response that's so bad that the speaker sounds bad once the frequency response is corrected.
> 
> The more important considerations in designing a speaker system are frequency response and directivity.


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