Help with Affordable Stereo HiFi Subs

[chunkster]

I have a pair of Thiel CS3.5's that are currently taken apart for recapping of the crossovers and a mid driver rebuild. The Thiels (when working properly) are lovely speakers but are not great sub 80Hz or so. I listen to a good bit of electronic/popular music (no sneering please )that reaches into the lower registers and would like to add a subwoofer or subwoofers to compliment my Thiels. I don't beat on my speakers in terms of volume but would like bass with impact and clarity at the lower end. This is purely for music so quality is more important than absolute volume or low end. I'm on a budget (as in the less money the better) and was wondering what's possible with a DIY. I've been playing with unibox and understand the basics of the different box designs and speaker parameters, but I'm really not sure why kind of F3's I should be looking for. I realize that most of the 20Hz stuff is typically for movies, but again, I do listen to pop music that gets pretty low (The XX - Crystallized is a good example) What should I be looking for in a driver? Cabinet dimensions are not critical. I could build a large cabinet if that's what's required. I'm seeking counsel from those of you much more experienced than I am.

Thanks!

 

[audiomagnate]

Infinity 1262w from Amazon is the cheapest out there AFAIK. I got a pair of really nice used PWH302 MB Quarts that work well in 6 cu ft sealed boxes for $75 a pop. Is that cheap enough?

Used car woofers can be had cheap on Craigs, but not many work well for home hifi. The two mentioned above do.

 

[chunkster]

Audio - That's more than cheap enough for me. I was thinking $500 a piece for drivers, amps and materials. What kind of frequencies are you seeing with those?

Thanks!

 

[chunkster]

Audio - Would you hook those Infinity's up at 2 Ohm or at 8 Ohm? If I ran them at 2, should I be worried about killing a Bash 500W plate amp?

 

[KaffiMann]

Would you hook those Infinity's up at 2 Ohm or at 8 Ohm? If I ran them at 2, should I be worried about killing a Bash 500W plate amp?

8ohm would give the amplifier a much easier load, you will get some small impedance variations anyway so the overhead will be better/realistic. A 2 ohm load is very tough to drive properly with any home amplifier. There is nothing to gain from running low impedance, you just deplete the current reserve of the amp faster, it may sound constrained pending on the load.

 

[chunkster]

Kaffi - It appears the Theil #'s for this sub were calculated at 2Ohm if I'm inputting these numbers into unibox for modeling what parameters do I need to change other than Voice Coil inductance and resistance?

Thanks!

 

[audiomagnate]

I agree with Kaffi, run them at 8. They are so cheap right now at amazon you could go swing some DSP in addition to a good amp since the cabinet will cost you next to nothing.There's a good thread here about a $500 sub competition with lots of good info.

My boxes model down 6 db at 20Hz.

 

[head_unit]

8ohm would give the amplifier a much easier load, you will get some small impedance variations anyway so the overhead will be better/realistic. A 2 ohm load is very tough to drive properly with any home amplifier. There is nothing to gain from running low impedance, you just deplete the current reserve of the amp faster, it may sound constrained pending on the load.

Absolutely! Never mind any specifications, we measured lots of amps and seldom found more than maybe 1-2 decibels of output loading them down, and a price of higher temperatures and reduced efficiency.

 

[head_unit]

What should I be looking for in a driver?

Hearing/feeling bass requires a lot of sound pressure, which means physically moving a lot of air. So there is simply no substitute for displacement. Some small woofers have very long strokes, but bigger woofers can move the same amount of air with less stroke (which "typically" means less distortion).

As for 20 Hz, that will encompass the vast majority of stuff. The trick is to be able to play it at a high SPL. Low frequencies played at low SPL are not perceptible, so there is no point in making a 10 Hz subwoofer unless it can play the 10 Hz quite loud.*

You can Google and find lists of special tracks that have lower frequency content.




*Louis D. Fielder and Eric M. Benjamin, "Subwoofer Performance for Accurate Reproduction of Music", Journal of the Audio Engineering Society, Volume 36, Number 6, June 1988, pages 443-456. this is quoted in
Threshold of Hearing - DiracDelta Science & Engineering Encyclopedia