Stereo Subs

[Luvin Da Blues]

Good Day Ladies and Gentlemen'

I am new to this site so... Hello Everyone.

I am posting this looking to tap into the vast knowledge I have been reading on this forum for awhile now.

I am looking for advice on my current setup.

I have mated two subwoofers to my bookshelf speakers. Each front channel consists of a Infinity Beta 20 bookshelf speaker that sits on a 11" custom riser (Cherry wood) and all this sits on a Infinity TSS750 sub. I have spent countless hours with my Rives test CD2 tweaking and optimizing them and got them sounding pretty good to my ears. The subs are fed from Denon AVR2500 using the Pre out/main in with a Y-connector. The sub crossover is set at ~100Hz.

I haven't yet implemented any spikes, isopads or bass traps yet. If anyone has any advice or comments I would appreciate them good or bad.

I listen primarily to blues, R&B and some classical and rock with music being the defining source for this setup.

Thank you in advance

[Dusty Chalk]

Sounds good -- sounds like you already know what you're doing, what do you need us for?

Oh, definitely feel free to start with bass traps -- lookup "Ethan Winer". Sounds like you already got the bass power for that.

What happens is, when you install bass traps, is that you sound like you lose bass power, because it doesn't resonate in your room as much. But what really happens is that you tighten it up, and you get your snap and prat back.

Or, just sit back and enjoy.

[Luvin Da Blues]

Thanks Dusty for the reply

I don't profess to be an expert on audio systems but try to listen and learn from all sources and try to make the best of my midfi setup until I can afford the "good stuff"

[Florian]

Hello there,

good choice on Stereo subwoofers. A good improvement over a single one. The only suggestion i have is that you might try a lower x.over point then 100Hz. Other then that, keep on rocking as Bernd used to say

[Luvin Da Blues]

Thanks Florian,

I started with a lower x-over point but, I graphed the freq response of the BS speakers and the sub separately and together and found a hole (-9db's) at 125hz (same for both channels) so I upped the x-overpoint to compensate. This helped somewhat.

I have a Behringer 1/3 octave Eq I could hook up to flatten this dip, should I turn down the x-over freq and try to correct with the EQ? Should I use the EQ for the sub only or for the BS speakers only or both?

Comments?

[blackraven]

Nice speakers the Beta 20's. I don't know why more people don't consider them considering their price and sonic performance. I think they compare well with speakers costing much more.

[Florian]

A 9db dip is quite a lot. You cant really correct that, and not at a critical frequency like 100Hz. Its funny, cause all Apogees have a 100Hz dip also. (the grand beeing a exeption). You can get rid of it with more distance to the sidewalls.

You can see a repsonce in my gallery or click here !! This responce is not with the right crossover and should not be considered final !! I run a Tact RCS 2.2XP room correction device. The bumbs are fully corrected. The big gap is from trying to integrate my temporary subwoofer crossover. But no dips ;-)

http://gallery.audioreview.com/data/audio//500/ms.JPG

You can see the 100hz dip from the right speaker, which you can fix with more distance to the sidewalls. Give it a try!

Ill do a new measurement for you later where you can see the difference.

Cheers

[Luvin Da Blues]

Thanks again Florian,

I'll give the new placement a go when i can get my lady out of the house for a couple of hours.

Thats a nice flat freq curve...Strange but I have a dip around 50Hz (-3db's) like you show on your curve also.
Is that graph from your room correction compensator? I would be interested in learning more about this technology..is this piece of equipment expensive? I live in a small town in Canada
and the local shops may not carry stuff like this..is it available online?

Again, thanks for your constructive comments.

[Florian]

Hello,

yes its fairly expensive. In my current configuration the room correction device (Tact RCS 2.2XP) is around 6K US. The curve currently is horrible in my room, but the Tact corrects all in 0.2Hz steps and 0.2db accuracy ;-) Flat from 6.5Hz on up.... will be much better once all the power amps and the 4 way computer controlled crossover comes in.

Cheers

Flo

PS You got PM

[AudioBack]

I know that two subwoofers is better than one. However one sub might be doing all the mid bass and the other is doing none or cancelling it out alittle. When I had my Monitor 9s as my mains, I found the speaker on the left was kickin the midbass and the right was kicking no midbass out. It made music sound like crap and the speakers exceptionaly bright. I then Put mini monitors in the front and crossed over my sub at 80Hz. My midbass problem went away. My sub was in the right spot to talk up to 80Hz and make the crossover point seemless with very minimal cancelation. My point is that my sub is on the left side of my room where bass response is good. If I had 2 subs with one on each side, I would get a huge dip just like the one I was getting with the monitor 9s due to the fact the one on the left would be doing midbass while the other would be doing nothing that would cause a massive dip. I'm not saying place the subwoofer on the left side like in my room. Every room has a spot that is optimal for bass response. I say find that spot and put both your subs in that spot. You may have to lower the crossover point from 100 to 80Hz to keep bass from being directional. Stereo subs is a cool idea, but room acoutics play a huge part on making that work. You may try to fight it with an equalizer, but then find you have tanted the sound that much more. Do what works for the room, not what works for you, and you will be alot happier. Yeah, my monitor 9s are in the closet until I can use them again, but now I can listen to my stuff without another bass test and knob turning session. I'll see if I can use the 9s when I get a more ideal room. I hope this has given you a cheaper alternative of getting rid of your nasty dip.

[Luvin Da Blues]

Thanks for the input AB,

I was wondering if this is caused by phase cancellation...your comments seem to reinforce this. What I was trying to achieve was to make bass cabinets for the Betas since their roll off point is a little high.

I was reading a bit about room modes lately so I metered the response at 125Hz in front of my listening position and behind and found that the level was so much better about 1Meter behind me but this could be a standing wave. I didn't measure other freqs around this yet, so I maybe just changing the freq at which this dip is occurring.

Damn it, now not only do I have to deal with correcting this dip but also have to completely rearrange my room...Thanks...Just joking.


One question, how did you determine which channel was down since this cancellation would only occur with both subs driven. When I drive them separately, after careful placement, they both seem to have the same freq response (+/- 2dbs)?

[Luvin Da Blues]

Just to add to this ..I am using an older Radioshack analogue meter with the Rives Test CD2 which is corrected for this meter...should I upgrade to a digital or newer meter or even a different brand...suggestions?

[AudioBack]

One question I forgot to ask. Do you have your Betas high-passed? If you don't, do that before you do anything. If you don't know what high-passing is, it is crossing over your main speakers to do no lower than a certain frequency. So if your sub is set at 100Hz, you should high-pass your mains to play no lower than 100Hz. If your stuff is not high-passed, then your problem is definately cancellation. If you have a modern surround reciever, it should be able to do this for you. If you do already have your stuff hooked up this way, let me know. If you don't we'll have to get you hooked up.

[Luvin Da Blues]

Hi AB,

No I don't have them hipassed and was wondering how to go about this...my older Denon AVR2500 doesn't seem to have this feature or a sub xover control but I'm using the subs crossover, unless I'm missing something in the onscreen display...maybe it's time to upgrade to the 3806 that I want anyway. Is anyone familiar with this unit(the 2500)?

Thanks for your constructive remarks and look forward to your reply

[AudioBack]

Ahhh, there's your trouble. I just looked up your receiver. It is too old. Definately time to move up to a 3806. Pro logic receivers cannot high pass. You must have a Dolby Digital receiver to do so. I have the Denon 2801 which is really old, but still does Dolby Digital. Man, upgrade and hear what you've been missing. Pro logic blows compaired to Dolby Digital. While you're at it, buy a coax or optical cable for that DVD player. You'll need it for DD. Let me know what you plan to do.

[Luvin Da Blues]

Thanks Again AB,

I would like to talk more on this but right now I have to get to work...I'll look for you online tonight when I get home

[Luvin Da Blues]

Sorry for bringing this thread up again guys but,

According to our friend AudioBack I absolutely need to highpass my bookshelf speakers in my setup.

Couldn't I just use the natural freq. rolloff off these speakers and match the subs xover to this point

I remain humble

[markw]

Couldn't I just use the natural freq. rolloff off these speakers and match the subs xover to this point

Some speakers, like my maggies, simply ignore any low frequencies they can't handle. I never needed a high pass filter when I ran them with a sub.

If yours are similar in that respect, then there's no need for a high pass filter in the circuit. Only if they audibly complain would I consider it.

But, if I might interject, I've always found that having a sub separate from the mains offered the benefit of allowing placement of the mains to maximize imaging, soundstage and other fuzzy adjectives pertaining to mids and highs and placing the subs (independently) where they could do the most good which, in my experience was NOT where the mains are. But, wives don't always like to hear that...

[Luvin Da Blues]

Thanks Markw..thats kinda what I was thinkin...but there's so much experience and knowledge in here I thought I would check anyway

[markw]

Thanks Markw..thats kinda what I was thinkin...but there's so much experience and knowledge in here I thought I would check anyway

Just make sure you set the cub's crossover to as low a frequencty as possible to avotd overlap.

I've always liked to use title song on Bela Fleck's "Flight of the Cosmic Hippo" CD. It has a great fretless bass run that's great for helping find the correct blend.

[Luvin Da Blues]

Thats TOO FUNNY...I just picked up that CD last weekend for the same reason...I heard it was recommended for the Bass lines

[Luvin Da Blues]

OK Ok I'm just a little dense but too many of you guys with vastly more knowledge than I have suggested that I abandon having my subs under the BS speakers and placing them where they will do more good so...thats exactly what I'm gunna do


THANKS GUYS