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#118354 - 12/03/05 04:58 AM Rane PE-15 for sub's room resonances
nitram Offline
buff

Registered: 04/09/03
Posts: 57
Loc: Santa Rosa, California
I thought I'd share my experience with a used but newly bought (on eBay) Rane PE-15 parametric equalizer. New $300, got it for $100 incl. shipping, and it has only cosmetic damage that's irrelevant to me since it's going under the furniture, right beside the sub amp.

http://www.rane.com/pdf/old/pe15dat.pdf

The Rane PE-15 is an analog parametric equalizer. It has 5 bands, with overlapping center frequencies of 20 to 300 Hz, 60 Hz to 1 kHz, 150 Hz to 2.5 kHz etc. Each band has knobs for filter frequency, bandwidth (0.03 to 1.5 octaves), and attenuation/boost (-15dB to +20dB).

I got it to get rid of nasty +20dB room resonances at 50 Hz and 80 Hz. See, because of the WAF, my Hsu TN1220HO is hidden behind a 6' armoire in the corner of a 23x13'x9' room, and the listening position is right in the center of the room.

I was thinking of getting the BFD, but I figured that playing with filter tuning knobs is more fun than programming digital. So when I finally won a PE auction at a price I was happy with (took 3 auctions and 2 weeks of trying), that settled it.

Anyways, the PE-15 looks very industrial, reminds me of the Hsu 500W amp. I just plugged the darn thing between the receiver and amp (using RCA to 1/4" mono cables from Radio Shack), fearing the worst (ground loop).

Sure enough, I plug it in, turn it on and there's a very very loud hum. $*%&@! I say to myself, but then it occurs to me that this is a used box, and the cables are cheap, so after some mucking with the connectors the hum just went away. (Probably just some corrosion on the contacts in the PE-15, so it wasn't a ground loop but a floating ground on the RCA cable going to the sub amp!)

I used a downward bass log sweep from the Boston Acoustical Society test CD, and used the two lowest frequency bands, one at a time. I set the center frequency by eye to 80 Hz, the bandwidth to the minimum 0.03 octaves, and the attenuation to -15 dB. I then tweaked the center frequency until it seemed (by ear and by Radio Shack SPL) that the notch filter was set to the center of the resonance, and then I backed off the attenuation factor and widened the bandwidth until it seemed reasonably flat. (Room resonances don't boost uniformly within a room, and there are many common seating positions either when we're using the projector or just listening to music, so perfection in any one spot is pointless.) I then did the same for the 50 Hz peak. There, I had to rely on the SPL more because deep bass is kind of hard to pick up by ear in any quantitative way.

Then, because the resonances were gone, I could boost the bass gain in the receiver way up to keep the SPL flat from mid to deep bass. OK, there's still resonances but boy going from 20 dB to 6 dB makes a world of difference.

A couple of notes:
1. I was able to drop the receiver cross-over from 150 Hz to 100 Hz. Believe it or not, it did sound better at 150 Hz before equalization.
2. The PE-15 was passing audible noise to the TN1220HO when the filter bandwidth was set too tight. (They warn that happens in their manual.) After tuning it went away. Plus, I activated the sub amplifier's built-in cross-over because the noise was coming at frequencies that the receiver wasn't sending anyways. Finally, I reduced increased the sub gain in the receiver and reduced the sub amp gain to improve the signal-to-noise ratio.
3. This kind of product I'm pretty comfortable buying used. These kinds of analog circuits are bombproof compared to typical consumer electronics, so it'll either work perfectly or be burned out.
4. Previously, to keep the bass from being ridiculously boomy at the resonances, the sub gain had to be reduced way down, and while the sub dramatically improved the overall sound compared to just the mains (M3Ti pair in each front top corner of the room), there still wasn't much punch where there was supposed to be, like with drums, and pipe organ pedal tones just seemed weak. Lower bass music (bass lines in jazz say) would have audible distortions in volume vs frequency too.

In summary, I feel that adding the equalizer made as much of an improvement to the bass over the M3Ti+TN1220HO as the addition of the TN1220HO alone did. That's what bad room resonances do, they force you to back off the bass, so my deep bass (20-40 Hz) was maybe 15-20 dB lower than it is now. Now, it's deep, rich, nearly uniform bass to the depths.

Best $140 (incl. SPL and cables) I ever spent!

--Martin

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#118355 - 12/03/05 08:32 AM Re: Rane PE-15 for sub's room resonances
F107plus5 Offline
connoisseur

Registered: 01/24/05
Posts: 2034
Loc: Fla. Orig. Mich.
Great report Martin!!

Thanks for opening the door to discussion of paraEQs(I had asked Axiom for a plate amp with built-in multi-band paraEQ in another thread about two days ago,...cool, huh?)

I had been looking at the PE-15 and the current PE-17(I think)as well as a discontinued Behringer, and find these things fascinating!

My current plate amp has the old fashioned single band semi-para EQ; simply swap out resistors to vary the attenuation/boost and frequency(yuck, hey,...it sorta works)now I just gotta get down to Rat Shack and drop my twelve cents into their coffers to get my newly replaced PE Titanic flat to 30(ancient sealed box)that is, if I can find my soldering iron.

I LIKE YOUR WAY BETTER!!! Cuz I still have about +9db at around 50(yeah, me too)to fight with, and if I attenuate that with resistor swaps, I'll lose the ability to gain what I need lower down,...Arrrrgh!

Yup, multi-band is the way to go!!
Rich.

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#118356 - 12/03/05 10:23 AM Re: Rane PE-15 for sub's room resonances
MarkSJohnson Offline
shareholder in the making

Registered: 09/27/04
Posts: 10830
Loc: Central NH
Martin:

Excellent report!

Coincidentally, I've been (finally!) setting up my BFD over the last couple of days and planned on reporting my results as well, but you did it so well that I'd be embarrassed to post now!

_________________________
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::

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#118357 - 12/03/05 11:23 AM Re: Rane PE-15 for sub's room resonances
bugbitten Offline
connoisseur

Registered: 04/06/05
Posts: 2339
Loc: Madisonville, KY
You! Embarrassed! Anybody posting their own picture like yours would be hard to embarrass!

Martin; Thanks for taking the time to post your results.



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#118358 - 12/04/05 03:43 AM Re: Rane PE-15 for sub's room resonances
nitram Offline
buff

Registered: 04/09/03
Posts: 57
Loc: Santa Rosa, California
You know, I think there's something to be said for a BFD-like level of control that a digital filter gives you, especially if you have multiple room modes. With adequate tweaking, you can get a flat enough response to impress fellow audio geeks with. But I think the multi-band filter approach was good enough to get rid of the few really bad room modes that dominated my room response. The BFD does have lots of cool LEDs (that's why Mark got it I bet), but I just love the tweakiness from the 6 pots on the 2 bands I'm using. (I'm an elec eng in case you can't tell.) So while Rich might like swapping resistors in and out, I think turning pots is a lot more fun. A purist might also say that analog will give cleaner sound than digital, but I doubt anyone can hear digital distortion in sub-100 Hz sound anyways.

And there's no sense getting too worked up about every last dB of resonance. Especially when you've spent only a total of $1500 on audio (cheap Panasonic receiver & DVD, used sub & PE, new Axiom M3ti & VP100). Jeez the audio armoire was more than that!

--Martin

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#118359 - 12/04/05 12:10 PM Re: Rane PE-15 for sub's room resonances
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3186
Loc: Toronto/New York/Dwight
Hi Nitram,

Excellent use of the parametric to reduce the worst of the room modes. Most subwoofer users (and many reviewers) have no idea of the huge variation in low frequency response below 100 Hz caused by the room. In a typical 2400 cu. ft rectanglar room, there will be 9 room modes with variations in response of up to 20 dB, even to different seating locations on a couch.

As you've demonstrated, it's possible to significantly reduce some of these resonances and smooth out low frequency response with careful application of parametric EQ.

Regards,
_________________________
Alan Lofft,
Axiom Resident Expert

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#118360 - 12/04/05 03:32 PM Re: Rane PE-15 for sub's room resonances
MarkSJohnson Offline
shareholder in the making

Registered: 09/27/04
Posts: 10830
Loc: Central NH
My setting up of the BFD seems to be a never-ending process of late. Everytime I think I'm on to something, everything gets changed around again.

I'm metering yesterday and keep physically tapping the meter because I'm not getting a reading at 95Hz and, like many analog meters, it sometimes sticks a bit. It's not coming back - no reading - and I know the batteries are good.

I'm sitting on the back of the couch during these tests so I can read the meter as it's in position for a person seated on the couch. I lean forward a bit and hear my tone volume drop. I lean forward further, putting my head alongside the meter, and the test tone drops out completely. Not "down a bit", but completely. I can't hear it at all.

My room sucks. At 95Hz, literally.

I'm resetting the BFD back to factory default (for the third time) and starting all over again, this time with two subs. I can't even imagine that in a room this size... a room that I thought would be too small for the 350.... I'm actually considering running two of them.

My room sucks.
_________________________
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::

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#118361 - 12/04/05 07:49 PM Re: Rane PE-15 for sub's room resonances
snakeyes Offline
aficionado

Registered: 07/13/04
Posts: 828
Loc: Newburgh, NY
Mark the one thing that is not clear from your post is
does your room suck?
_________________________
------------------------------------------------
Leave the gun, Take the canolis.

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#118362 - 12/04/05 08:14 PM Re: Rane PE-15 (WIDE PHOTO)
MarkSJohnson Offline
shareholder in the making

Registered: 09/27/04
Posts: 10830
Loc: Central NH
From ten minutes ago. Yes, my room sucks.

_________________________
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::

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#118363 - 12/04/05 08:37 PM Re: Rane PE-15 (WIDE PHOTO)
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 17739
Loc: NoVA
So....


your room sucks, then?
_________________________
I didn't do it, no one saw me, you can't prove anything.

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