DIY subwoofer: what does it need?

[Feanor]

I'm considering building a pair of subwoofers -- actually "super woofers" might be a better description -- and I have a crossover design question.

The drivers will be Dayton Reference 10" High Fidelity Sub models, see here ...

http://www.************.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-460​

They'll go into sealed enclosures.

Signal will come from the integrated amp's pre-out connections and through Behringer crossover to my old Phase Linear 400 amp and thence to the speakers. See the Behringer I intend to use ...

http://www.************.com/pe/pshowdetl.cfm?&DID=7&Partnumber=248-664​

So the question us given I'm using the Behringer active crossover, do I need to need to include a Zobel impedance compenstion filter as I would with a passive crossover design??

 

[Feanor]

Humm?? Links don't seem to work

Any tips? Does Audioholics hate Parts Express?

 

[Sheep]

One member works for them and shamelessy advertised all over the forums for free.

They were offered a nominal fee and the right to use their link as much as they want, but they declined. So no links.

SheepStar

 

[MacManNM]

I'm considering building a pair of subwoofers -- actually "super woofers" might be a better description -- and I have a crossover design question.

The drivers will be Dayton Reference 10" High Fidelity Sub models, see here ...

http://www.************.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-460​

They'll go into sealed enclosures.

Signal will come from the integrated amp's pre-out connections and through Behringer crossover to my old Phase Linear 400 amp and thence to the speakers. See the Behringer I intend to use ...

http://www.************.com/pe/pshowdetl.cfm?&DID=7&Partnumber=248-664​

So the question us given I'm using the Behringer active crossover, do I need to need to include a Zobel impedance compenstion filter as I would with a passive crossover design??

The short answer to your question is, no. You don't need a compensation filter. That amp shouldn't have any problems with those drivers. Is there a reason that you are going with that particular driver? What are you trying to achieve with this setup? Just curious.

 

[Feanor]

My intended application

I intend to use the subs for a couple of possible applications, both stereo rather than HT.

First, I want to use the sub pair to extend the bottom end of my Magneplanar MG 1.6QR's. The 1.6's would run full range, and the subs below about 40Hz. I think this setup calls for a very fast, distortion free bass, hence the sealed encloser and these particular subs that are tauted as very low distorion.

Eventually I might use the subs to provide the bottom end to some 2-way DIY project, say below 150 or 200Hz. I was dreaming along the lines of a Accuton C92-6 mid/bass with an Accuton C23-6 tweeter in a sealed enclosure.

 

[MacManNM]

I intend to use the subs for a couple of possible applications, both stereo rather than HT.

First, I want to use the sub pair to extend the bottom end of my Magneplanar MG 1.6QR's. The 1.6's would run full range, and the subs below about 40Hz. I think this setup calls for a very fast, distortion free bass, hence the sealed encloser and these particular subs that are tauted as very low distorion.

Eventually I might use the subs to provide the bottom end to some 2-way DIY project, say below 150 or 200Hz. I was dreaming along the lines of a Accuton C92-6 mid/bass with an Accuton C23-6 tweeter in a sealed enclosure.

Well those drivers will be perfect for that type of usage.

 

[Feanor]

Thanks!

Well those drivers will be perfect for that type of usage.

I appreciate your input.

 

[WmAx]

I intend to use the subs for a couple of possible applications, both stereo rather than HT.

First, I want to use the sub pair to extend the bottom end of my Magneplanar MG 1.6QR's. The 1.6's would run full range, and the subs below about 40Hz. I think this setup calls for a very fast, distortion free bass, hence the sealed encloser and these particular subs that are tauted as very low distorion.

A ported enclosure is perfectly capable of producing distortion free bass, and because of the significantly reduced excursion at lower frequencies, the non-linear distortion of the driver will actually be reduced using a ported system. The term 'fast' in reference to bass is an oxymoron. How are the slowest cycling frequencies be 'fast'? 40 Hz is 40 Hz. If it's faster than 40 Hz, it's no longer 40 Hz!

It's all about frequency response! Most sealed enclosures have a constantly rolling off low end starting at around 40Hz. I can take a parametric equalizer, make two measurements(one of a sealed target response and one of the ported system), then apply a transfer function using the parametric equalizer and make a ported enclosure sound exactly like the sealed enclosure -- except the ported enclosure will have a greater SPL/dynamic ability.

Of course, it's easier for the general person to just make a sealed box and have it sound 'fast', I suppose, as compared to applying a transfer function as I suggest above.

-Chris

 

[Feanor]

I take your point about "fast", but ...

What do you mean about "applying a transfer function"? I'm ignorant of course, but to me that's techo-babble

 

[MacManNM]

A ported enclosure is perfectly capable of producing distortion free bass, and because of the significantly reduced excursion at lower frequencies, the non-linear distortion of the driver will actually be reduced using a ported system. The term 'fast' in reference to bass is an oxymoron. How are the slowest cycling frequencies be 'fast'? 40 Hz is 40 Hz. If it's faster than 40 Hz, it's no longer 40 Hz!

It's all about frequency response! I can take a parametric equalizer, make two measurements(one of a sealed target response and one of the ported system), then apply a transfer function using the parametric equalizer and make a ported enclosure sound exactly like the sealed enclosure -- except the ported enclosure will have a greater SPL/dynamic ability.

Of course, it's easier for the general person to just make a sealed box and have it sound 'fast', I suppose, as compared to applying a transfer function as I suggest above.

-Chris

Actually you are correct, Chris, when I ran my code on this unit last time, I made an error. This unit would perform extremely well in a small-vented enclosure. Around 2 cubic feet is all it would need, with a couple of ports. Although for this application I would apply an electronic high pass filter around 28Hz (I’m assuming he’s a 2ch vinyl man).

 

[WmAx]

What do you mean about "applying a transfer function"? I'm ignorant of course, but to me that's techo-babble

Basicly, that means to apply equalization in order to re-shape the frequency response to a specific target response.

-Chris

 

[Feanor]

Interesting: box size, etc.

For the Dayton Ref. 10" sub HF model, my BassBox Pro program tells me that the closed box should be about 0.7ft^3 while the vented would be about 1.6 ft^3 -- either of these is doable for me.

But for clarification, various stuff I have read suggests that closed box give the best transient response (-- maybe that relates to the "fast" adjective). Do you guys agree? Or will a vented box do basically as well??

 

[MacManNM]

For the Dayton Ref. 10" sub HF model, my BassBox Pro program tells me that the closed box should be about 0.7ft^3 while the vented would be about 1.6 ft^3 -- either of these is doable for me.

But for clarification, various stuff I have read suggests that closed box give the best transient response (-- maybe that relates to the "fast" adjective). Do you guys agree? Or will a vented box do basically as well??

Fast is a bad way to describe it. I believe when people use that term, they are describing the ability of a sub to "hit hard" as in a kick drum. The problem with your driver is that in a sealed enclosure there isn't much useable bass under 40 Hz, whereas with the vented unit you can achieve a flat response down to 28 or so. You can use a simple EQ to correct the sealed unit and increase the low end response, or you can depend on room gain. You are going to have to use some type of EQ for both in all probability. I would build one of each and see which one you like.

 

[Buckle-meister]

Excuse me for jumping in here, but I've a question to you MacManNM:

Most sealed enclosures have a constantly rolling off low end starting at around 40Hz.

If, as WmAx suggests, a typical sealed enclosure rolls off below approximately 40Hz, then how would using...

...a simple EQ to correct the sealed unit and increase the low end response...

...help? I mean, wouldn't you be asking the EQ to boost the signal, and if so, isn't that anathema (meaning that EQ's are for lowering peaks, not raising nulls)?

Regards

 

[MacManNM]

Excuse me for jumping in here, but I've a question to you MacManNM:



If, as WmAx suggests, a typical sealed enclosure rolls off below approximately 40Hz, then how would using...



...help? I mean, wouldn't you be asking the EQ to boost the signal, and if so, isn't that anathema (meaning that EQ's are for lowering peaks, not raising nulls)?

Regards

It depends, A parametric EQ is a great tool for fixing room nulls and peaks. A graphic or parametric can be used to help out the response of a box. The standard rolloff of a sealed enclosure is 12db/oct, one can apply a correction factor to that easily, because it is very predictable.

 

[WmAx]

...help? I mean, wouldn't you be asking the EQ to boost the signal, and if so, isn't that anathema (meaning that EQ's are for lowering peaks, not raising nulls)?

Regards

It depends on the mechanical capabilities of the woofer and the SPL required at at a given frequency. In fact, some subwoofer have inherantly almost no LF response, but are heavily equalized. You are sacrificing efficiency and SPL for size. However, today woofers exist that have excess power handling and mechanical abilities than would be normally required, lending to make this technique possible. Many years ago such mechanically capable woofers did not exist. If you are interested in the general technique of compensating a sealed box response, refer to the Linkwitz Transform circuit. For targetting a target response by electronic compensation, refer to compliance scaling. Despite the apparently biased (and unsubstantiated) opposition to equalization that some hold, they are indespensable if the highest level of control and refinement is desired.

-Chris

 

[WmAx]

But for clarification, various stuff I have read suggests that closed box give the best transient response (-- maybe that relates to the "fast" adjective). Do you guys agree? Or will a vented box do basically as well??

I believe what you are referring to is the general rolloff rate. It is true that by definition, a closed box has the best inherant transient response. By the same token, a 1st order crossover has the best transient response so far as crossovers are concerned. However, no credible evidence exists that demonstrates this transient response difference as a lone variable is audibly important. People tend to draw premature conclusions based on too little evidence. I already outlined one possibility why most sealed boxes may sound 'faster' than most ported boxes. But you can easily replicate this rolloff taper with electronic means. In the end, this means that someone can potentially change the complete bass characteristic of their system with the push of a button or use a more efficient system(ported but replicating sealed response).

-Chris

 

[Feanor]

A fastinating discussion!

I have no objection at all to using equalization; in fact, that was more or less my intent, though I'm not exactly sure what topography or equipment I would use.

BassBox predicts -3dB at 32Hz for vented or 42Hz for sealed. Interestingly, if the Qtc is set to .6, (rather than .707), -3dB is at 40Hz; I've heard the lower Qtc gives even better transient response, though the box size increases to 1.1ft^3.

I guess I could use 1/3 octave equalizer to boost the response above 22Hz, the Fs. Below that I suppose a cut-off filter would be prudent. Any thoughts??

 

[WmAx]

I guess I could use 1/3 octave equalizer to boost the response above 22Hz, the Fs. Below that I suppose a cut-off filter would be prudent. Any thoughts??

A 1/3 octave fixed equalizer is not likely to produce optimal results. You require a fully adjustable parameteric equalizer. [Note: I should not have to say fully adjustable parametric, since this is seemingly redundant, but many recievers seem to have so-called parameteric equalizers that are not fully adjustable)

-Chris

 

[Buckle-meister]

Thanks WmAx and MacManNM.

It depends on the mechanical capabilities of the woofer and the SPL required...

So would it be true to say that if one has no idea of the mechanical capabilities of one's speaker's woofers (and/or electrical capabilities of one's amp presumably), one should use EQ only to lower peaks, not to raise nulls so as to prevent the potential overstress of either?

Regards