Suggestions for dual Mid woofer wiring setup

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Hello to everyone . I am currently using the Audiopipe APSL8 a 8" mid woofer at 8 Ohms in a sealed box in a tri-amp set up , all amps are solid state fed from from a DBX "Driverack PA" processor and have another spare pair of the same 8" drivers that I'm thinking of installing in the same cabinet wired in parallel which would bring them to 4 Ohms . Would leaving them wired in parallel and reducing the amplifier output work well or would I have to install a resistor of some value ? My knowledge of resistors is very limited . Thanks Pete

[DeZZar]

Generally speaking if you double up the drivers wired in parallel without changing anything else in terms of the box or tuning of the box you will of course gain somewhere around 3db in output for the same power, half the impedance and reduce cone excursion.

HOWEVER, you materially change the Q of the box. You'll actually loose some bottom end bass extension (less so in a sealed enclosure but still a consideration), alter group delay (possibly not negatively), and most importantly the change in impedance is likely to alter the behavior of the crossover and any filters. Not to mention that you now have increased output that is out of balance with the rest of the drivers in the system.

4ohms just means the speaker will demand twice as much current from the amplifier for the same voltage. If the amp is up to it, it shouldn't be a problem - and most amps are.

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Thanks for the insight . I prefer to keep the box sealed but I'm not sure if I should make dual 0.4 ft3 chambers for each driver or double up the internal size into a single cavity 0.8 ft3 . At present my current mid bass has no passive filter and is crossed over through my DBX processor in the range of 90 - 1000 Hz with no Eq , will group delay pose a problem with respect to the frequency range as for the the increased output I can adjust it either through amp output Bryston 3B or the processor output .

[DeZZar]

So what are you actually looking to achieve with the additional mid-woofer?

Generally the main reasons to double up woofers/mid-woofers is one or a combination of the following:
- increase overall sensitivity to match other higher sensitivity drivers in the system (i.e. a tweeter)
- increase power handling of the system
- alter/create a particular directivity characteristic of the system

Given the APSL8 is only running 90-1000Hz and is capable of handling 200W RMS (full range I assume) I hardly think you have a power handling issue to solve? And its already 95db sensitive. You'll be close to 100db sensitive with two of these in parallel - can the woofers and tweeter keep up with that?

What's the application - live music?

[fpitas]

The drivers can share a double-size cavity if they are paralleled, or be in separate cavities: your choice. I'm kinda curious what you're trying to achieve, too.

[a4eaudio]

Generally speaking if you double up the drivers wired in parallel without changing anything else in terms of the box or tuning of the box you will of course gain somewhere around 3db in output for the same power, half the impedance and reduce cone excursion.

I'm kinda curious what you're trying to achieve, too.

You will gain 3db sensitivity for doubling the drivers and another 3db for halving the impedance for a total gain of 6db.

This could be a good thing, but fpitas has a good question on what you are trying to achieve. You would typically want to double the volume of the box AND you will need a tweeter that can match the increased sensitivity.

[fpitas]

Not sure I understand the group delay question, either. You will get a very distinct polar pattern if you stack the midbasses, but that's just the interference pattern between them.

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I'm looking to create a bigger sound field within my system (Audio Bliss) . I have a large music room with plenty of amps and no "Wife Approval Factor" issues , being semi retired allows me the time to seek more sound experimenting , furthermore I did some research on group delay which shouldn't be a problem .

Thank You for the advice to all . Pete

[fpitas]

Good luck Pete, but multiple drivers actually narrow the sound field because of interference. Think MTM or line array.

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I chose the setup as MTM , I would like to attach some pics of the build but I haven't figured out how to compress the file yet . Cheers to Music

[fpitas]

As mentioned above, your tweeter may not keep up with the increased output from the woofers. I guess you can series them if that's the case.

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It should be as simple as reducing the output from the either amp or DBX crossover , as mentioned before the Mid's have no passive filters . Thanks Francis .