Strength In #'s - Rule???

[Loud & Clear]

I've forgotten the general rule of multiple woofers. Say you have a woofer that responds to 35hz @ -3db. Ok now you put another with it. What is your low response then? Say you stack four of these things? I can't believe, I can't remember... :o:

[Robh3606]

If you are talking mutual coupling with subs it would be 6db for the pair and 9db for 4 or 2 pair. As far as referenced to a midband level -3db at 35hz won't change all else being equal. You would have to raise the midband level to match if we see where I am going or lower the subs. You are going to gain output over a range where they couple depending on wavelength, distance and placement.

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=626


Rob:)

[Loud & Clear]

If you are talking mutual coupling with subs it would be 6db for the pair and 9db for 4 or 2 pair

Rob:)Actually I was talking frequency (low) response. I know the more woofs you put together, the usable lowest freq. is lowered... :)

[Robh3606]

Not really. Just adding more of the same woofer doesn't change your bandwidth. Will improve you power handling but won't make it magically go lower. You would have to change box tuning, add EQ or tailor summed response.

Rob:)

[Loren42]

The output power sums when you add woofers in parallel. I think it is a 6 dB gain for two in parallel. However, that is across the whole frequency band.

So it just gets louder across the board.

[Loud & Clear]

I'm almost certain, when grouped, the usable low frequency responce is lowered... I know about the ad a woofer of the same kind, in the same inclosure, up 3db. It's the frequency response I question... ;)

[Mr. Widget]

I'm almost certain, when grouped, the usable low frequency responce is lowered... The operative term is usable response. My personal experience agrees with Rob's post. Now perception or perceived response may not directly agree with actual measured response.


Widget

[Allanvh5150]

Generally I have found that a single bass driver in a particular cabinet volume tuned for optimum flatness, is identical to 2 of the same driver in double the enclosure volume. The whole senario will be up 3dB on the single driver. Mutual coupling is a huge variable and I always leave it out of the equation. If I gain something extra all well and good. However......As evidence by many JBL cabinets and my own findings If you double the driver count and make the enclosure bigger you can tune it lower. Most of the JBL designs specify 5Hz lower for double drivers.:)

Allan.

[JBL 4645]

If you are talking mutual coupling with subs it would be 6db for the pair and 9db for 4 or 2 pair. As far as referenced to a midband level -3db at 35hz won't change all else being equal. You would have to raise the midband level to match if we see where I am going or lower the subs. You are going to gain output over a range where they couple depending on wavelength, distance and placement.

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=626


Rob:)

Also it’s twice the cone area coverage as well.

The sub bass nearer to the floor might have few dips in some places peaks as well that can be cut with EQ.
The sub bass above it might fill in the few dips with few tiny peaks and it might have dips in the lower part of the frequency response.

That’s one thing I’ve twigged onto now.

[Ian Mackenzie]

Typically you will get more usable bandwidth because of the increase in displacement and lower distortion. That equates to less power compression.

The problem is it represents a lower impedance load (half the impedance for two woofers in parrellel) to the amplifier and the amplifier has to be able to deliver the required current. This usually results in more heat from the amplifier.

[Loud & Clear]

Thanx for all the replies gentlemen... I know that corner placement up's the out put vs. just room placement. I don't know if frequency comes into play or not. I know it's an odd thread... :bouncy: