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General speaker questions for audio and home theater.

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RE: EQ and subs? a continutaion from K-Bob's learning.

Posted by Presto on May 7, 2017 at 13:03:38:
Here is my take.
Over the years I have set up lots of budget systems, sometimes using things for pre-amps and amps most 'philes would not consider (or tolerate).
The 6000C seems to be a decent choice for running (2) four ohm subs in stereo. 500WPC into 4 ohms stereo and at 55 pounds, one can probably assume this amp has some good damping factor characteristics (aka, good size supply rail capacitors and transformers, which are important for Class AB amplifiers like that. (Class D amps can weighing 10 pounds can delivery 1000W..)
The push pull amps use 10" drivers and are 88db 1w/1m sensitive?
What is the impedance of each driver in the box and how are they connected?
If you provided the specs (or at least model) of each driver, someone could better help getting the most out of that specific combination of amps and boxes.
To figure this out you want to try and estimate the maximum power output of each box and how much input power is required to get there. This will help you decide which amp to run on which boxes.
The HK is a good amp, but remember that 60A peak power (likely total, and not per channel else they would have said so) at 8 ohms is 240watts per channel peak. Not as impressive sounding... This is not rated for four ohms (no specs given) but is four-ohms capable.
So what's the plan here? Put the larger amp on the more efficient boxes to maximize output? Or put the bigger amp on the less efficient box to try and have some sort of level matching this way? The HK probably does about 150W/ch at 4 ohms... maybe 175. It won't double with a damping factor of 150. You need to get into 750+ numbers to do that. (Also, this damping factor could be averaged over a range of the spectrum... this is often done. An amp with a damping factor of 500 at 250Hz can be below 100 at 50Hz.)
Next calculation is to see, for each connection option, which unit bottoms out first in each case. I bet the 6000C could drive either pair of subs to full excursion, possibly without even clipping. In the case of the HK, I would bet the amp starts to suffer first, with the PS rail voltage getting dragged down considerably during heavy bass power surges. This can lead to the kind of distortion that can cook woofer coils, or cause excessive heating in the amp, but worst of all, distorted uncontrolled bass. The opposite of tight, clean bass. (Once you've heard super-powered amps and high quality woofers that don't "thump" but can actually pound and *hit*, when you hear loose distorted bass it makes your skin crawl.
There is really one question here: given the type/nature of each sub box and each amp, is there a way to best match them up, OR is using both pairs and both amps not going to be an optimal solution anyways?
Do you have separate circuits to the room? If both sub amps are on the same circuit, I would not have the HK and the less sensitive box dragging down the AC supply voltage if only delivering a smaller chunk of the over-all SPL.
I suppose the "multiple subs for smoother response" will be a factor in this, but I have a feeling the HK amp will be a limiting factor and possibly even do more harm than good depending on how your audio room is circuited.
Cheers,
Presto