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-   -   How much compromise, small EQ'ed sub (http://www.diyaudio.com/forums/subwoofers/98069-how-much-compromise-small-eqed-sub.html)

audiobomber 14th March 2007 02:31 AM

How much compromise, small EQ'ed sub
 
I have a pair of Rocket UFW-10 subs (1 cu ft sealed enclosure, 10" doped aluminum woofer, 500W amp, single-point EQ). http://www.audioholics.com/reviews/s...rchterm=ufw-10

To extend response, the little Rocket subs use 12 dB of EQ. How much compromise is this design, compared to a pair of BESL XLS subs? http://www.bamberglab.com/xls.shtml

I'm not concerned with extension. I only care about music, so 30 Hz is good enough, but I am concerned with quality. Is a small EQ'ed box with a plate amp very much of a compromise compared to a high quality discrete amp and the BESL subs?

I crossover from BESL S5-MTM's at line level, 70 Hz LR4. I am very happy with the bass performance now, and spending a lot more money is probably idiotic, but I might be tempted if it's going to make a significant difference. http://www.lakefly.com/images/MTM-sub.jpg

AAaF 14th March 2007 07:40 AM

It is possible to get a faster AND lower bass reproduction. See http://www.linkwitzlab.com/filters.htm#9. You can see that just about everything is changed to the better.

MJL21193 15th March 2007 12:59 AM

As with all small subs, the only compromise in this one may be box size. The designer has compensated for this with a powerful amp and equalization. EQ is not the demon everyone thinks it is and 400 watts peak power is the same from a plate amp as from a discrete amp, especially at lower frequencies.
The MTM speaker above it - is it vented? If it is, it may conflict with the sub in that there could be some cancellation and overlap as the sub is not vented. Worth checking out.
These subs are expensive! And you have two of these? They should be more than adequate for music IMO.

audiobomber 15th March 2007 12:48 PM

Quote:

Originally posted by MJL21193
As with all small subs, the only compromise in this one may be box size. The designer has compensated for this with a powerful amp and equalization. EQ is not the demon everyone thinks it is and 400 watts peak power is the same from a plate amp as from a discrete amp, especially at lower frequencies.
The MTM speaker above it - is it vented? If it is, it may conflict with the sub in that there could be some cancellation and overlap as the sub is not vented. Worth checking out.
These subs are expensive! And you have two of these? They should be more than adequate for music IMO.

The BESL monitors are sealed, f3 about 70 Hz, and I roll of the main amps feeding the monitors with an inline passive filter, -3dB@70 Hz, BW2. As a result my subs are functioning more as a woofer than a sub, crossed over at 70 Hz LR4.

Thanks for your comments on small EQ'ed subs, that's the kind of thing I'm looking for.

audiobomber 15th March 2007 01:01 PM

Quote:

Originally posted by AAaF
It is possible to get a faster AND lower bass reproduction. See http://www.linkwitzlab.com/filters.htm#9. You can see that just about everything is changed to the better.
I already have most of what the Linkwitz active filters offer. The subwoofer amps are EQ'ed by the manufacturer to +12 dB at 30 Hz and are essentially flat to that point. The sub controls include level and XO point, plus a single point EQ with controls for frequency, Q and level (+6 to -15 dB). Very useful for dealing with the main room mode.

The main amps feeding the MTM monitors are rolled off at 70 Hz, using FMod passive inline filters, which I find are more transparent than my Marchand XM44 active crossover. The Marchand is sitting on a shelf, unused.

http://www.hlabs.com/products/crossover/

richie00boy 15th March 2007 01:09 PM

Quote:

Originally posted by MJL21193
The MTM speaker above it - is it vented? If it is, it may conflict with the sub in that there could be some cancellation and overlap as the sub is not vented. Worth checking out.
Sorry that's wrong. You don't need a vented sub to suit vented speakers, nor a sealed sub to suit sealed speakers. All you need is the appropriate low-pass filter on the sub to suit the main speakers, be they sealed or vented.

As for the original question, it really comes down to how the EQ is implemented. If it's plain simple boost then there is room for improvement.

audiobomber 15th March 2007 02:11 PM

2 Attachment(s)
Quote:

Originally posted by richie00boy
As for the original question, it really comes down to how the EQ is implemented. If it's plain simple boost then there is room for improvement.
I'm not sure what you mean. Can you elaborate?

Here's the manufacturer's built-in EQ. I'm also using the sub's single point EQ to cut the room mode by 4dB. I'll shortly be adding a pair of FMod filters to cut subsonics and further trim the room mode.

audiobomber 15th March 2007 02:18 PM

2 Attachment(s)
Quote:

Originally posted by richie00boy
Sorry that's wrong. You don't need a vented sub to suit vented speakers, nor a sealed sub to suit sealed speakers. All you need is the appropriate low-pass filter on the sub to suit the main speakers, be they sealed or vented.
And yet I've heard some people I highly respect say that the mains should be sealed for proper integration with a sub. Is that because of the phase changes the signal undergoes with a ported speaker? I know that the audibility of phase changes is a controversial topic.

Here's the free air response of the UFW-10 from the Audioholics review.

audiobomber 15th March 2007 02:25 PM

Quote:

Originally posted by MJL21193

These subs are expensive! And you have two of these? They should be more than adequate for music IMO.

Are you referring to the typo on the Audioholics site, where it says MSRP $4999? :D

The Rocket subs are very inexpensive, $999 for a pair. In fact I don't see how they could be diy'ed for any less.

richie00boy 15th March 2007 02:38 PM

Quote:

Originally posted by audiobomber
I'm not sure what you mean. Can you elaborate?

Here's the manufacturer's built-in EQ. I'm also using the sub's single point EQ to cut the room mode by 4dB. I'll shortly be adding a pair of FMod filters to cut subsonics and further trim the room mode.

What I mean is that a plain and simple EQ (which looks like what you have) can be bettered by a Linkwitz Transform.

Quote:

Originally posted by audiobomber
And yet I've heard some people I highly respect say that the mains should be sealed for proper integration with a sub. Is that because of the phase changes the signal undergoes with a ported speaker? I know that the audibility of phase changes is a controversial topic.
You have misunderstood what they meant. The integration aspect is simply what I said about matching the sub LPF to the main speakers. Most subs have a 2nd-order LPF (simply as this is loads easier to make than a variable 4th-order one), so match best with sealed main speakers with a usually fairly complementary 2nd-order response also.


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