Newbie - Basic Questions

**Spadez** · **10-15-09, 11:28 AM**

That size is my maximum, in an ideal world Id have it 17"x17"x17" (or around just under 2cu.ft)

Im also trying to find the supplier of these subs in the UK, but im not having much luck.

**Mike P.** · **10-15-09, 12:13 PM**

If 17"x17"x17"is ideal for you then consider the Peerless XXLS 12".

http://www.hometheatershack.com/foru...adiator-2.html

http://www.hometheatershack.com/foru...on-sa1000.html

**Spadez** · **10-15-09, 12:56 PM**

If I did want to keep with the 15's and was willing to give up a bit more of my floor space, what would you recommend a Dayton 15"?

**Mike P.** · **10-15-09, 01:23 PM**

It depends on how much floor space you're willing to give up and which 15" Dayton. Your previously mentioned maximum box size would be more suited to a 12" ported. If 17"x17"x30" is the maximum size then we can compare 12" ported against 15" sealed to see which wins out.

**JCD** · **10-15-09, 02:50 PM**

I've heard good things about Dayton's Titanic subwoofer drivers.

Here is a modelled response for their 12 and 15 inch drivers in a close and vented box.
If you look at the graph, starting from the left and working your way right, you have:

15" vented -- green line -- in a 10.4cu ft box
12" vented -- pink line -- in a 3.3cu ft box
15"" closed -- red line -- in a 5.0cu ft box
12" closed -- yellow line -- in a 1.5cu ft box

**Spadez** · **10-15-09, 04:36 PM**

Im really suprised at the graph, it seems like I would be missing out on some deep tones if I go for a sealed design.

**Mike P.** · **10-15-09, 04:41 PM**

Yes, ported would have more output in the low end. Notice the box sizes that it takes to achieve that.

**Spadez** · **10-15-09, 04:43 PM**

What is your opinion on passive radiators, since these seem to be able to achieve good sounds with a small box design.

Also for the volume calculatior, would you say 0.5cu.ft. is a fair value for a standard 15" driver volume?

EDIT: One more thing! In music, what is usually the lowest Hz levle that would be in the song. I know this is an incredibliy open ended question, but if tones lower than 50Hz arnt normally included then it makes a difference to my sub setup.

**Mike P.** · **10-15-09, 05:27 PM**

PR's work well with subs that require a small low tuned cabinet. .25 for 15" driver volume is close enough. Music is usually considered to go down to 30 hz.

**JCD** · **10-15-09, 06:38 PM**

Just a quick comment on PR -- I have nothing to back this up, but from what I've heard it's REALLY hard to get a sub with a PR right. One guy I know who used to design speakers for a living said he never could get it right.

And do you mean 5.0cu ft for a 15" driver? If so, I'd guess that's a good enough ballpark for a 15" driver in a sealed system. If you mean 0.5cu ft, then no, way too small.

As for the low end, I think one could argue that 40hz may be a reasonable low end for music. The really deep stuff is typically only found in movies.

**fredk** · **10-15-09, 09:39 PM**

Quote:

As for the low end, I think one could argue that 40hz may be a reasonable low end for music

Depends on the music. The loswest note an an electric bass is around 41Hz. Classical music has a number of instruments that reach down to the low 30s and stuff like pipe organ and synth can reach well into the teens.

**the_diyr** · **10-15-09, 10:54 PM**

Simple put I think using a car subwoofer , people find you get a better product fo less money.. I have looked at my 10 inch yamaha sub that cost about 130.00 bucks.. The sub is nothing more than a paper cone woofer, it's sad.. I could have taken about 50.00 more bucks and had twice the sub.. When I first got my Pioneer A/V reciever I didn't have a powered sub so I used an old JL audio 12 in a sealed box with a 200 watt pioneer amp rigged up to a computer power supply and it sounded really good.. The only reason I went with the Yamaha powered sub was that it was alot less ugly and I was to lazy to build another sub box.. But to each his own.. I saw a bunch of plate amps on sale at ebay the other day I think they were Klipsch if this helps any.

**Moonfly** · **10-16-09, 04:18 AM**

Quote:

Spadez wrote:

Im really suprised at the graph, it seems like I would be missing out on some deep tones if I go for a sealed design.

That is one reason that I'm using 2 drivers in my sub, I want to keep the sealed design, but my sub will have to be twice the size of the one you want to build. In a small room you will get good performance with a sealed sub, but that will change when you move to your bigger room which may be a consideration for you.

Have you considered a flat pack MK sub from deep surplus? It'll give cracking performance in a reasonable small enclosure and musically they are about the best sub Ive heard so far. Its the sub that made me sell my SVS sub.

**the_diyr** · **10-16-09, 08:34 AM**

http://shop.ebay.com/?_from=R40&_trk...All-Categories

Lot of Dayton subs on Ebay today ??

**Mike P.** · **10-16-09, 09:31 AM**

Probably B stock with no warranty.

**Spadez** · **10-16-09, 11:47 AM**

A few more "newbie" questions to add:

These amps that ive been seeing people put in the back of the sub, are they only if you dont have your own stand alone amplifier, or is it if the stand alone amplifier doesnt have the power needed to power the sub.

Is it a good idea to cover the inside of the sub with sound absorbant material (if yes, can you recommend some?) or is it dependant on the application?

When putting a grill over the top of the sub, is it a good idea to leave some room between the normal state of the top of the sub and the back of the grill incase it hits.

**Moonfly** · **10-16-09, 12:14 PM**

You can use a plate amp, built into the sub, or you can use a slave amp of some sort. Most people will use rack amps like the Behringer EP series as they are cheap, and give massive amounts of power cheaply. Having the amp separate can make box construction easier, (a sealed sub is the simplest design too BTW), but if you dont want things separate then a plate amp will keep things together.

You dont need to insulate the inside of the box, and many well known manufacturers dont bother, but almost all will use some kind of fibre fill. You can use either, of both if you really wanted, but as long as your box is constructed well everything will be fine.

When making the grill, you need to work out a minimum clearance. For this look at the xmax of the driver, then give yourself a bit of extra room beyond this to make sure the driver doesnt contact the grill. Whilst contact probably wont hurt the driver occasionally, it'll ruin your sound.

**Mike P.** · **10-16-09, 12:45 PM**

The advantage of a plate amp is most have a built in Hi-Pass filter (rumble filter) which protects the sub from over excursion at the lower frequencies. Some plate amps have boost like 5 db at 25 hz or 6 db at 30 hz as an example. This you don't want for your setup. Read the specs, it will say if the amp has boost or not.

Pro amps like the Behringer are cheap and have lots of power, but Pro amps don't have the Hi-Pass filter that is required at the lower frequencies. An add on unit would be required like the Reckhorn B2..

http://www.reckhorn.com/index.php?ln=en&prod=b2

**Spadez** · **10-16-09, 01:23 PM**

Thank you for explaining that to me. If i used a plate amp for my sub, what would i use to power my mids / trebbles?

You also say "This you don't want for your setup", why is that?

**Mike P.** · **10-16-09, 01:32 PM**

Your receiver powers the main speakers, the LFE output from the receiver sends a signal to the plate amp which in turn powers the sub.

Quote:

You also say "This you don't want for your setup", why is that?

In reference to the Passive Radiator Peerless design you linked to in your other thread, that design is not meant for any boost from the amplifier.

**Spadez** · **10-16-09, 01:41 PM**

Ah ok. So im guessing the difference between a receiver and an amplifier is that an amplifier is designed to drive the bass directly?

Can I still use a plate amp and receiver combo, but just not use "boost" from the amplifer? Wouldthis be a good decision.

P.s Thank you for answering all my questions, I know these questions must be like pulling teeth.

**Moonfly** · **10-16-09, 02:21 PM**

An amplifier powers speakers. A receiver in the context of an AV(R)eceiver is a processor and amplifier combined. The Receiver part processes incoming signals from your DVD player etc, the amp bit powers any speakers you add to your system. A sub is part of your system and comes in two variations. Passive subs are powered by the receivers amps, an active sub is powered by its own dedicated amp.

Bass tones are power hungry, and work speakers hard, especially small ones. So, to avoid massive amps and speakers, the active sub was invented. This is a single large driver, powered by it's own amplifier, to take all the strain of producing these bass tones from your main amp and main speakers. A nice side effect is that speakers that arent trying to produce sub bass tones become clearer and can handle more volume.

Sub bass (under 80hz) is omnidirectional, in that your ears cant locate its origin. This is why a single sub works in a system, and why it can be placed anywhere in your room, conveniently out of site

. The thing with sub bass, is that it can act funny in your room. This is why plate amps sometimes include features to help with room integration, and this is why people like to use them. They are a little more costly than rack amps though, which is why people requiring a lot of power will try and use them.

**the_diyr** · **10-16-09, 07:43 PM**

Quote:

Probably B stock with no warranty.

I agree probably are B stock ... As for a warranty Hmmm.. I have bought so many subs that said 1 year warranty.. My last was a Sony.. the actual cone broke loose from the spider when it was delivered I called sony to explain and was told that they didnt warranty that type of problem because it was obvious the sub had been mistreated .. funny thing was I never hooked it up just noticed the cone broken loose when I unpacked it .. But I do agree about B stock ... and now that I look again the prices are not that great ..

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