Making a sub louder using electronic filters e.t.c

[bob123]

Hi,
I have a twin 15" sub that i use for parties with some PA mains that i have built.

I also have a 2 x 500w(rms) 4ohm TOA power amp.

Firstly there is a slight problem that the amp can only put 250w into each driver as the impedance is 8ohms. Can this be solved? the amp is bridgable but this would make things worse and cause huge amounts of heating e.t.c. As its load would be equivelent of driving 2ohms per channel.

Secondly i am currently using some basic 741 based filters inorder to filter out +300hz and -20hz so i can get the most bass. But i think the roll off is only 3db/6db per octave which is not very good for such a small bandwidth. Is there a better filter that would work?

Is there a way of electronicaly enhansing the music so that the frequency that causes a feeling in your chest could be maximized?


BOB

[Khron]

I think some kind of parametric EQ would suit your needs just fine.

http://sound.westhost.com/project63.htm
http://sound.westhost.com/project75.htm
http://sound.westhost.com/project84.htm

These links should be a good place to start, and maybe with a 4th order Linkwitz-Riley active band-pass (hi-pass @ 20Hz, lo-pass @ 300Hz), should get you where you want

[simon5]

To get the full 500W, buy another twin 15" subwoofer if you can. Only way to solve it would be to rewire the coils to be a 4 ohms load.

[AndrewT]

Hi,
your opamp based bandwidth filters are more likely to be 2pole giving you 12db/octave slopes beyond the -3db cut-off frequencies.

Can you post a schematic?

Your present wiring is giving you 250W + 250W into the cabinet 500W total.

If you change to bridged your 500W + 500W into 4ohm amp becomes 1000W into 8ohms. The total power available is identical whether bridged or separate.

If you need more SPL from this amp then the only way is to change drivers or add an extra cabinet to run each cabinet as a 500W ohm version.

My preference is to accept the lower distortion of your present set up.

[lndm]

To give you stronger sounding bass with higher power handling and greater sensitivity, you might consider putting the woofers in a smaller box.

I was reading in another thread someone commented that the body cavity resonated at 80Hz. If this is in fact true, your task may be fairly simple. More 80Hz could be had by the above method, or by room positioning (which I think you should try anyway), or with an active filter and it wouldn't stress the amp like infrasonics would.

[Bazukaz]

Hi,
Smaller box gives better sensitivity , but lowest frequencies start to roll of earlier.If the design is optimised for high SPL , it may be okay.But , if one wants the best bass extension , larger box , in my opinion , is a better choice.
6 th order bandpass also has good sensitivity , but not so good transient response.
A bass horn is an overkill in size but is very efficient.

Regards,
Lukas.

[bob123]

I just would like to increase the spl of the bass around the area that humans are more susceptable (sp?).

If i bridged the amp and ran that into 4omhs would the max output be greater than just running the 2 channels into 8 ohm speakers?

The amp has short circuit protection and clipping monitors. I am just curious that if the current is double than what it should be and the output is kept below the clipping would that be greater than if it was running normaly?

As for the filter it is single pole HP followed by a single pole LP.
therefore i assume it is 6db/oct

[simon5]

You have better damping usually with higher ohm speakers, so doubling the current usually doesn't increase SQ.

Let me explain what choices you have with your amplifier.
500W into 4 ohms and 500W into 4 ohms
or
250W into 8 ohms and 250W into 8 ohms
or
1000W into 8 ohms.

You have two speakers at 8 ohms each.
In parallel it will be a 4 ohms load.

The only way you'll get the full 1000W is powering only a single speaker with the amplifier in bridged mode. Problem is you'll have the same loudness in theory when powering both speakers with 250W each. In fact, a single speaker with 1000W will be less loud because the coil will overheat versus two speakers with 250W each. You'll have better reliability and lifespan too for both the amplifier and the speakers.
1 speaker at 1000W = 2 speakers at 250W each so 500W total. (2 times more speakers but 2 times less power)

You can bridge your amplifier and run both speakers, the amplifier can now in theory deliver 2000W, before something break, and something WILL break. At lower volumes, you'll not have problems, but I doubt you can reach 1000W without problems because current will be at 15.8 amperes at 1000W and it's made to tolerate 11.18 amperes.

A good solution is building another TOA amplifier so you bridge an amplifier into each speaker, so they both get 1000W. The other solution is to get a second subwoofer cab.

Building a 2nd amplifier will give you a gain of 6 dB in theory. (4 times more power delivered)
Getting a 2nd cab will give you a gain of 6 dB in theory. (2 times more power and 2 times more drivers)

A second cab is the best idea for reliability and lifespan but the second amplifier is a good idea if space is restricted.

[simon5]

BTW to tweak the bass I suggest using a parametric EQ or something similar.

If you have the space for a bass horn, that would increase the bass human feels a lot like Bazukaz suggested.

[lndm]

6dB, or slightly less in practice, isn't the biggest difference unless you are almost there to start with. I know it's been said already but where you put your speaker in your room will cause a cancellation pattern that may remove the bass you're looking for.