Paradigm sub with VOTT

[acre]

Greetings all.

I have a question regarding my Altec speakers and a Paradigm Servo 15 sub in a Home Theatre arrangement. My problem lies in getting the correct blend between the Altecs and the Servo 15. My L/R channels are the Altec A-7-800's in 10 cubic foot domestic cabinets, thanks to Dave Fitts and GM! (15" Eminence Kappa Pro LF have sucessfully replaced my 416-8A; that's another story.) I'm driving these with a 6 year old Sony 5.1 amp, 110 watts per channel. The L/R channels are set to "large" while the rest of the system is set to "small". I've tried setting the mains to "small" but it really doesn't help. The room is 22'x34'. I sit about 16 feet back from the system. ( When I sit at the 32' mark, the blend sounds real good. Perhaps the wavelengths of the Servo 15 are too long for the 16' mark.) The room is in the basement and completely finished with drywall, carpet and suspended ceiling. The room is quite "dead". When the sub kicks in it does the tricks it's supposed to do but it just isn't what I classify as "musical", either on movie or CD playback. I've gone through the exercise of placing the Servo 15 where I sit and listening for the smoothest bass response and then moving the sub to that spot. The controller unit for the Servo 15 has a variable phase dial and frequency cutoff. I currently have it cutting off at 100 Hz. The sub is fairly close to a corner beside one of the Altec cabs. I had a PSB Sub-Sonic 6 (12" driver, vented) prior to the Servo 15 and it sounded much better. I'm I getting too much bass? Perhaps I'm saturating the room despite its large size.

The Eminence 15" do make a good replacement for my 416-8A as a stand alone cabinet. I've managed to get the phase correct between the LF and 811B horn. So please assume for now that the full range cabs are performing well.

Your help and input would be very much appreciated. Many thanks folks!......Lee

[bfish]

Hi, acre!

I can't help much, as I'm pretty HT illiterate, but had a similar experience with a Sony STR-DE675, and several speaker configurations. When I found satisfactory settings for movies, music sucked. Finally gave up and went to separate systems, great music, adequate HT.

Good Luck!

[DonM]

In 10 cu ft cabinets your LF drivers are probably reaching close to 40hz. Your sub crossover at 100hz maybe too high. Have you tried reducing the crossover?

I too have the same Altec drivers and am struggling with the alignment between the 806a and the 416's. Could you just briefly comment on how you set yours up?

[acre]

Thanks for the notes guys. BFish, I too have been told by a high end audio store (where I got the Servo 15) that the Sony is the weak link in the chain. I may have to take this up with them. I'll let everyone know what I find.

As for you Don, I'd be glad to send pics of my speakers. For now, you see that I had to switch to new bass drivers. One of my 416-8A had a bad rub in one of the voice coils and both spiders have become very weak over the years to the point that the punchy bass once heard 30 years ago is all but gone. Frankly, the 416 would probably make a good passive driver for a low output sub, given the correct box. At any rate, GM advised me to set my x-overs to about 8 on the dial. The LF driver is mounted as close to the horn as possible without weakening the baffle. Here's the trick: I found that there was a pretty sharp peak at about 900-1,000 Hz, real close to the x-over drop off point. To eliminate it all I did was tip the 811B horn forward on a bit of an angle and it did the trick! Now it seems that no matter how loud I push the speaker, there is no fatique factor anymore. I also have a LeSon tweeter in parallel with the HF driver. (I'm I correct in my assumption that your from the Toronto area? I got these LeSon tweeters at Long and McQuades, Oshawa. They were 12.00 each) Phasing of the LeSon's is not a problem as they respond from 18,000-23,000 Hz. They are a bullet tweeter. If you need pics and dimensions send me a private email and I'll be happy to help. I'd post them here if I knew how.....regards.....Lee

[GM]

Greets!

A couple of observations........... You don't want 'dead' in any audio app except an aneochoic chamber, and a good servo sub has extremely low distortion, so folks tend to describe their performance as 'dry', 'sterile', etc., ergo don't mate well with any resonant ('musical') speaker alignment. Try blocking off the vents, and if it requires too high an XO point (ideally you don't want to go higher than 80 Hz), then just damp them as needed.

BTW, the WLs from both systems are the same size in the XO BW, so assuming the sub and mains are 'close enough' acoustically on the same horizontal plane, there's no mismatch other than probably level. Note that regardless of XO point/slope used, this layout dictates the sub connections either be reversed or the phase control set around 180 deg..

GM

[acre]

You're right on the money GM! I found a good tone generator on the Audioholics forum that produces tones in 1 Hz increments from 20-300 Hz. I burnt these files to a CD and used them to set the phase controller on the Servo 15 so that my db meter registered the maximum level/frequency. It would seem that if the Servo 15 is set 120 degrees out of phase with a 100 Hz cut-off, the result is a very smooth and musical bass sound. I've managed to leave the ports open on my mains, as well. Your advice and comments, as always, are much appreciated.......Lee