Buying a subwoofer amp.

[Indybird]

Ok, so I am looking to get this subwoofer amp (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-804) to power this subwoofer (http://www.tb-speaker.com/detail/1208_03/wt-644f.htm).

I have a question about the amp; does any one know what the frequency response is (or is that only dependent on the speaker)?

Thanks,
Indybird

[Luke122]

That amp has an adjustable crossover built in, so you can dial in whatever cutoff you want for the sub.

The sub lists 32-600hz, so as long as you keep the amp within that range using the crossover, you are golden.

A tip though.. keep the sub running below 100hz, (I prefer below 80hz if your main speakers can run that low) to keep the location of the sub invisible in your room.

[NightrainSrt4]

Thanks Luke. I was just wondering pretty much the same question for my new Onkyo setup. The receiver had settings for sub 100hz up to 1Khz and I wasn't sure what to use so I just stuck with what was default. Now to look up the sub and put it towards the lower end.

Thanks. +rep

[Luke122]

Hey, no worries.

Bass below 100hz is typicall non-directional. Huh? The wavelengths are so long at low frequencies that it can be difficult or impossible to determine where the sound is coming from. Just look at car stereos.. you can often hear low bass much sooner than you can tell where it's coming from.

If your main speakers can play as low as 100hz, then set your sub cutoff at 100hz. Then just match the volume of the sub to the speakers, so it sounds like all the music/sound is coming from the speakers. If the speakers will play to 80hz, set the sub to 80hz.

Most home theatre front speakers are not designed to play as low as 80hz, though some will say that they have 40-20khz range, or something like that. Ideally, we need to know not just the frequency response of the speakers, but the variance in volume as well.

IE: 40-20khz, +/- 3db would mean that the speakers can play sounds from 40hz (very low bass) to 20khz (the upper end of human hearing), with a difference of +3 or -3 decibels across the range.

Most bookshelf/desktop/small speakers are more likely to run 100-20khz or even 150-20khz, +/- 5db, which means huge variance in output and very little bass.

This graph is for a Totem Arro floorstanding column speaker, my current object of lust.

http://www.audio-ideas.com/reviews/loudspeakers/graphics/totem_arro_freq.jpg

Notice how it drops off towards the left (low frequencies) and then again towards the right? That means lower bass is quieter, and so are extreme highs. The highs are not a big deal, since most people cannot hear all the way to 20khz (including me). The lack of volume for bass is somewhat obvious if you see the speaker.. not exactly a big driver on there.

http://www.totemacoustic.eu/imageswoodsample_arro_en.jpg

This is where a subwoofer comes in; filling in the lower end of the spectrum.

An ideal speaker would be 0-infinity, +/- 0db... as flat a line as possible. This is where the term "flat response" comes from, and yes, it's a good thing. No variation of levels across any frequencies, but certainly nothing like that exists as of yet.

[NightrainSrt4]

I can't seem to find the specs for the 200 series speakers, but I did find a page that had the woofer information.

I can't find the variance info, but the frequency response for the woofer is stated to be 27Hz - 150Khz. So now to find what the speakers sit best as.

Edit: Found a bunch of places trying to sell the service manuals for the speakers, but that doesn't help me much. Ughh, lol.

[Luke122]

Got any more details on the speakers?

[Indybird]

First of all +rep for the answer.

Second...I have another question. Is it ok to use car subwoofers for a home audio/home theater setup? I can buy a 10" Infinity Subwoofer for ultra cheap off of a friend, but I'm not sure if that was a good idea in terms of making a quality home subwoofer.

Thanks,
Indybird

[Luke122]

You can use it, there's just a few things to consider.

First, car audio subs tend to be very low sensitivity.. you need more power to make them loud. Second, they usually have very limited frequency response.. Focal used to make one model called "The Mule" that was only good from 30-60hz.. no joke. Third, they usually are lower impedance (4ohms instead of 8ohms), so if your amp can drive a 4 ohm load, you are in good shape.

Have you got the model of the sub, or any info on it? Will you be using the sub amp you linked to originally?

That amp will run a 4ohm sub with no problem, but since it's only 240w rms, you might not have enough power to drive the Infinity sub loud enough. Details on the sub will help make a good choice here. :)

[Indybird]

Here is the product page (http://www.infinitysystems.com/car/products/product_detail.aspx?prod=1020W&CheckProduct=Y&Language=ENG&Country=US&Region=USA).

I like this one because of the frequency response. I definitely wanted some thing that could go <30Hz. In the higher end I only need it to go to 110Hz, so I'm fine there. I however, don't know anything about the sensitivity, so maybe you could fill me in there.

-Indybird

[Luke122]

The sub is listed at 90db/w/m efficiency, which is actually quite high for a subwoofer of this style.

The manual for the sub also shows enclosures too, which is nice. You'll know exactly what to build to get the best output from it. If you are going for sound quality for music purposes, go with a sealed enclosure. For home theatre, go ported. Bandpass enclosures can be the loudest, but you really sacrifice quality for output.. I'd say stick with either sealed or ported.

I think you'll do well with this combo. :) Dont forget the build log!

[Indybird]

The sub is listed at 90db/w/m efficiency, which is actually quite high for a subwoofer of this style.

The manual for the sub also shows enclosures too, which is nice. You'll know exactly what to build to get the best output from it. If you are going for sound quality for music purposes, go with a sealed enclosure. For home theatre, go ported. Bandpass enclosures can be the loudest, but you really sacrifice quality for output.. I'd say stick with either sealed or ported.

I think you'll do well with this combo. :) Dont forget the build log!

Actually I'm going to put this speaker and the amp in a dead Logitech Z-5500 Subwoofer enclosure. I'll definitely put up a build log though.

Thanks again for the help, I'd like to give you more rep but I can't yet.

-Indybird

[Luke122]

If the enclosure is larger than the recommended volume, be sure to add something to take up the extra space; an old phone book wrapped in tape is a good filler.

If the enclosure is too small, add some foam/fiberglass insulation to simulate a larger enclosure. :)

[Indybird]

If the enclosure is larger than the recommended volume, be sure to add something to take up the extra space; an old phone book wrapped in tape is a good filler.

If the enclosure is too small, add some foam/fiberglass insulation to simulate a larger enclosure. :)

The original speaker that was in that enclosure was a 10" 188W speaker that was 5.4" deep, so I'm guessing this should fit about the same. Logitech already had some kind of fibery material in there that im guessing is for the same purpose as you are describing.

Anyway I'm gonna buy the speaker soon, and I'm ordering the amp today.

-Indybird

[Outlaw]

If your run a car sub and amp, make sure you have a solid power supply. I was running 2 12" solobarics (square speakers) off a 2000W Amp. The power supply was rated 25A, when the subs hit hard, it would spike past. Obviously if this were constant there would be an issue, but I guess its more of an FYI. They sounded real nice though :D

[Indybird]

I forgot to ask about the port issue:

I will mainly be using this for music, but my enclosure has a ~4" port. I have two questions:

First, if I want better lows (<40hz) and/or more responsive bass, is the port good or bad?
Second, if I don't want the port for music, could I simply stuff it with foam?

Thanks again,
Indybird

[Luke122]

Ports typically let you play lower/louder than sealed enclosures, but sealed enclosures are ultimate for sound quality. Yes, you can plug the port with foam or something. :)

[billygoat333]

the way that ported/sealed was explained to me was sealed was for tighter, more concise bass, (kind of like a kick drum) and ported was more boomier. So it all depends on the sound you like :)

[Indybird]

Well I got my amp in, so now I'm just waiting on my new reciever.

Another problem came up however. Though I don't plan on upgrading them any time soon, but I was researching new drivers for the surround speakers. Mind you they are currently the standard logitech speakers. Here (http://www.tb-speaker.com/detail/1208_03/w3-871sc.htm) is the exact driver they use. Now heres the part that worries me: Logitech states on their site that their surround drivers are 62W RMS @ 8 Ohms, when the driver is actually 12W RMS @ 8 Ohms.

http://techfuzion.net/DanishDevil/Z-5500SoundRoom/specification.jpg

What is going on here?
Is logitech grossly exaggerating these speaker's power?
Is there something else going on that I don't yet understand?

I'm mainly asking because I was about to hook these speakers up to a 70W (per channel @ 8Ohms) receiver and am now worried about damaging them if I turn it up at all.

Thanks,
Indybird