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SunnYii 17th May 2007 03:07 AM

Questions for DIY home Subwoofers
 
Hi Guys,

I'm pretty to this DIY home subwoofers, however I have previous experience with other DIY products. Before I decide if I want to buy a subwoofer from local store or DIY I would like to ask a few questions.

If I do decide to DIY a home subwoofer I'm going to get:

1. 350W RMS AMP Plate rated at 4ohms
2. 2 x 10" Subwoofer (Car subwoofers around 350RMS each at 2ohms or 4 ohms, I have not decide which one to get maybe something a little lower in power ratings)
3. Other parts needed to build the woofer box.


Questions:

1. Will Car subwoofers work on a home AMP Module (AMP Plate)?

2. If it does (which I think it should as long as we follow the ohms rules) do car subwoofers are rated the same way as home woofers. i.e. 350W RMS Amp is liek a mid range power for home subwoofers but for cars 350W RMS are nothing. Does that mean they are differnet?? In addition, since my amp plate only rated at 350W RMS is that means I should not get anything thats more then 350W RMS?

3. I would like to know if I have 2 subwoofers connected in series 4ohms + 4ohms = 8ohms then connected to the amp module it should work as long as the amp ohms are not lower then the woofers?

4. will 2 subwoofers in 1 box connected in series have better sound then 1 better quailty subwoofer? Due compression etc?

5. if I have 2 350W RMS woofer connected to the amp module is that means the amp module will not produce enough power for the woofers and it will under power which leds to distortion? (woofers will be connected in series but in reverse connections so bass waves will not get cancel out)

Thanks a million guys.

aceinc 17th May 2007 03:56 AM

I think I can answer your questions, but read my commentary at the end;

1) Yes

2) Yes, but, some mfrs are a little more generous with their specs than others.

3) Yes, but most plate amps are rated at 4 ohms. If you hook up an 8 ohm load you'll get about half the power, ~175 watts RMS.

4) The woofers should be connected;

amp+===+speaker1-===+speaker2-===-amp

under powering a driver in and of itself will not cause distortion, overdriving the amplifier will cause clipping, which will sound nasty, and can damage the woofers.

<commentary>
The first sub I built was a full size Decware "Wicked One" using two 10" Sony Xplods and a 350 watt Rythmik Audio plate amp. It had a WAF of -10, and after I putzed around with it it would put out large quantities of low freq sound. I didn't have test gear at the time so I can't quantify what I had. I can say that it seemed rather slow and boomy, but that may have been the room. So yes you can build a sub using car woofers.

I have since built two other subs, one using a Dayton 12" DVC using a PE 250 watt sub amp. I designed a ported cabinet using WinISD, and it seems much faster and more controlled, I now have test gear and it has an in room F3 of about 28 hz. I sounds quite good until I really crank it, and I would recommend it for an inexpensive DIY sub for a smallish room.

My most recent endeavour I describe it here I sounds great in my 3,400 sq ft living room, very controlled, and when needed it makes itself known.

Using car sub drivers will work, but there are a number of pitfalls;

1) MFRs of these drivers are notorious for not providing enough or reliable specs. This makes designing the sub hit or miss.

2) These drivers tend to have higher FS because car listeners listen to music which generally doesn't need freq's below 30hz. Home subs tend to be used for both music and home theater, which can have sound below 20hz.

3) Due to cabin gain, the smaller the box you are in (a car) the less energy it takes to reach a specific sound pressure, car woofers tend to be less efficient. Remember when picking a driver that 3db of SP level = a doubling of power. In other words a driver that gets 90db 1 watt 1 meter driven at 100 watts will generate the same SPL as an 84db 1 watt 1 meter driver driven at 400 watts.

So the short answer is, be vewwwwwwy caeful (as Elmer Fudd might say) when choosing the drivers, or you won't get what you hoped for.

</commentary>

If you state your goals and budget, there are lots of folks here that would be happy to help you buld something great.

Paul

MJL21193 17th May 2007 04:15 AM

Quote:

Originally posted by aceinc
[B I sounds great in my 3,400 sq ft living room, very controlled, and when needed it makes itself known.

[/B]

Hey, thats a small auditorium, not a living room! 34' x 100'? That's only a couple hundred square feet less than my whole house.

aceinc 17th May 2007 04:41 AM

My bad, that should have read 3400 cu ft room...

Paul

Stewart8989 18th May 2007 01:00 AM

I too am looking into sticking an old car sub into box for my home. The driver is the 12 inch Seas Lotus driver. I was looking at this amp Dayton Amp Do any of you have any experience/know about that amp, or any reccomendations would be great. Thanks.

Collo 18th May 2007 06:52 AM

You might be interested in this.....

http://www.subwoofer-builder.com/bl-...-final-opt.JPG

I live just up the road from you, in Newcastle, and have a sub that uses the same amp and two 10 inch drivers.

It's been superceded by a monster IB setup, so I guess I should sell it.

More info here

Drop me a line if you're interested in this piece of Aussie audio history!

regards
Collo

dangus 22nd May 2007 05:57 AM

I suspect that car subs are rated in the same imaginary watts that car amps are advertised with. Looking at voice coil diameter, and whether the pole piece is vented will give some idea of the real power handling.

There is some overlap between home subs and car subs; play with some response modelling software and see whether it can do anything useful in a sealed or vented box.

That Dayton sub amp is attractive but you can get a new Behringer EP2500 for less money than that. The EP2500 is a 2-channel amp so you could run stereo subs; the fan is fairly quiet. It also has clipping indicators and limiting so you'll know for sure when you've run out of power. There's probably other "made-in-China" "pro" power amps that are worth considering and that may be more available in your area.

SunnYii 23rd May 2007 06:32 AM

Hey Guys~~

I have been reading alot of these woofers and things lately...

so can anyone tell me what would happen if my amp module rated at 350W RMS @ 8ohms and I put 2 dual coil 4ohms (4 + 4ohms) together...would the amp run out of power and cause early distortion??

the reason for this it is because im in Australia Sydney. there arent much amp modules available, actually...the only one available it is the 350W RMS....nothing really get higher then that....plus it is kinda $$$ compare to what you can get in the US.

Collo 23rd May 2007 08:16 AM

With two voice coils, each of four ohms, you can connect them in three ways.....

In series for a total of 8 ohms. I'm assuming you're referring to the Jaycar 350w amp. It will deliver 240 watts into 8 ohms.

In parallel for a total of 2 ohms. That amp is not rated for 2 ohms.

Single coil only driven, for a total of 4 ohms. The amp will give 350w - you would need to be sure that the single coil is rated at 350w.

The different connections each produce different T/S parameters. See here for conversions.

aceinc 23rd May 2007 02:16 PM

Wouldn't two dual 4-ohm drivers give you a 4 ohm load? If driven series parallel such as;

amp+===+d1vc1-===+d1vc2-===-amp
&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;& nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nb sp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp ;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;& nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+===+d1vc1-===+d1vc2-===-

d1vc1 = driver 1, voice coil 1

This should make each driver 8 ohms, and when attached in parallel it should yield a 4ohm total load.

Paul


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