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I just recieved my subwoofer from Legacy. It's the LFExtreme. I'm very pleased. It has more power than I can handle below 100Hz.

Here's the problem. My mains have now gone from the first best to third best speakers in my room. The problem is I'm lacking mid-bass. Between 500-100Hz.

I just picked up a good book on speaker building. So, what I plan to do is build woofers to add to my mains. I'll probably bolt them to the bottom of my mains if they aren't too tall.

So that I need from you guys is speaker recommendations. Not really brand, but size, etc. What are the important theil-small numbers for this type of speaker. I have 120Watts of power into 8ohms for my mains now. So, I should have enough power. What size? I think 8-12, right?

My room swallows bass, so it needs to be tight and loud. What kind of enclosure? My book has all kinds.

Thanks for the help.
A more basic question

Pixie: have you balanced the SPL levels of your new subwoofer with your mains? This is a pretty basic thing that lots of folks overlook. Rather than having poor low bass, your subwoofer could just be set too high. Grab a <a href="http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F002%5F003%5F018%5F000&product%5Fid=33%2D2050">RadioShack SPL meter</a>, a <a href="http://www.stryke.com/">disk with some test tones</a>, and run some signals through your speakers. Don't forget to <a href="http://members.tripod.com/~terryctheater/shivaphotoalbum/page11.html">correct for the meter rolloff</a>.

You didn't mention that you balanced the output levels, so I thought I would suggest it...
I did exactly that. The sub even has an adjustable notch filter for 8' ceilings. Very handy.

It hovers around 80-90dB for the entire audio spectrum except for around 130Hz where it dips to 70dB.

I know I'm being picky, but I imagine quite a lot of Foley stage effects are around that frequency.

Here's another question

Pixie: Here's another thought. Where were you standing in relation to your speakers when you made the SPL measurements? This dip could also be a result of intereaction with your room. Try measuring SPL with the meter 2-3" in front of your drivers, vs measuring them from your seating position in the room.

If the dip still exists even when measured 2-3" from the driver, then maybe its time to look for a replacement. If the dip only shows up from your seating position (<a href="http://www.facstaff.bucknell.edu/esantane/mass12.jpg">like mine does with my sub</a>) this indicates that you need to move your speakers and/or seating position around a little bit. I had a 15dB dip between 45 and 80 Hz that I was able to flatten out by moving things around a little.
I have very little wiggle room for my mains. If I move them back anymore, they will be behind the plane of the entertainment center and TV. Maybe a couple inches either way will solve my problem.

You may be right about the interaction. The only parallel surfaces in my theater are the ceiling and floor. Someone do the math, is 130Hz a mode of 8'? I would guess that if 34Hz is, then 136Hz would be too.

So, the answer is to either create a notch filter for my mains or add more power by adding a speaker.

I'm itching to find a reason to build a speaker if you can tell.

Can anyone answer my original question?

Thanks Eric, you've been helpful.

Some Drivers...

Pixie: I realize the itch to build, just wanted to make sure you didn't overlook to "obvious" with your current speakers. Over the years, I've realized these little details can sometimes make a huge impact on the sound of your speakers.

Anyhow, as for mid-woofs, you might want to have a look at the Scan-Speak 18w-8545 and the 8545k version (kevlar driver). These are typically regarded as among the best mid-woofs available. <a href="http://www.northcreekmusic.com/#LoudspeakerKits">Northcreek</a> and <a href="http://www.bamberglab.com/s45k.htm">BESL</a> (both highly regarded diy kit producers) both use these in their top of the line speaker kits. They seem to run about $145 each.

[Edited by Eric on 05-22-2001 at 08:34 AM]
OK. I've rearranged my speakers and moved them around as much as I can. I have completely got rid of the hole at 130Hz, but created a much worse one at ~65Hz.

It's about from 56Hz to 70Hz At 56 and 70 it's 100dB, then it drops to 70dB around 65Hz. That's a very deep hole!

The rest of the spectrum looks good. What can I do about this? Obviously, it's a positioning problem. Isn't there a better way to figure out where to put my speakers?

Separate sub and mains?

Oh man! Solved one problem only to create another - sorry to hear this happened! With the new sub you are running, isn't this frequency produce by the sub rather than the mains?

If not, I'm not sure how to balance this one, I suppose this is one of the reasons why people argue for separate mains and sub that can be positioned independently.
Actually, I have an old decoder. It doesn't have a small speaker setting for the mains. The center does and the surrounds are always considered small. So, in short, yes the mains are part of the solution/problem at 65Hz.

I calculated the hole for a 8' ceiling. It would be 69.72Hz. That's almost exactly what I see. My test CD doesn't have that many frequencies, but it's close.

So, If I place my mains 1/4 of the height of the ceiling from the front wall, or 2' then they should reinforce that frequency, right?!

Hey, that's logic! Any bets on whether it will actually work?


I think it took it from -30dB to -24dB. That's nice, but this is very annoying.

I tried switching my sub on and off. My mains are very weak bellow 100Hz. They aren't helping the sub at all at that frequency. So, I tried to move the sub around. That didn't make a difference at that frequency.

So, I'm back to listening to music and trying to find the best spot for solid sounding bass. That could take months.

Doesn't anyone have anything to say on this subject? It seems like people are posting all sorts of new subjects to talk about. They get one response and then that's it. What happened to the nice discussions we we're having?

Some more thought about nulls

Pixie: Sorry to hear that your problem still persists! It looks like you are dealing with a room-induced null at that particular frequency. This is one that new drivers and equalization cannot fix..

I thought I remembered reading that the best position for speakers was at multiples of 1/3 of room dimensions, not 1/4. Of course, placing speakers 1/3 of the room lenght out from the wall will get almost anyone into trouble! The only thing I can suggest is to keep playing with the position of the speakers.

Good luck!
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