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Discussion in 'Speakers' started by Nick>P, Jun 21, 2004.
anyone know where i can find full reviews on the b4-plus?
Check SVS' own Web site; there they list a good number of links of reviews done on several of their subwoofer models, including the B4+...
"...hi, my name is Frank...and am an SVS bassaholic..."
It will be a while before I get a full review done... but I have done a lot of measuring with the same software, microphone, and methods that Ed did in his PB2-Ultra review... and a lot of listening to it, and to date, several other highly thought of subwoofers... Full review around Sept. 1... Any specific questions ?
From some recent HT-SPOT threads, it looks like you are switching to another test rig? What are your user impressions of the hardware and software, and how do the measurements compare to the other rig? TIA.
Ed - The new software (ETF) is more for indoor measurements of speakers... right now I am still more comfortable with subwoofers outdoors through the TrueRTA... and all the B4+ measurements have been done using it...
The ETF software allows quasi-anechoic measurements by eliminating room effect... it is pretty cool for that, you can actually see in the response curve when the room effect occurs by the milli-second... and then make adjustments accordingly.
As of now, I think the over 200 Hz is working fine... to within 1 dB of anechoic... but the bass stuff needs more work.
The microphone was calibrated +/- 1 dB from 9 to 30K Hz... and up to 140 dB ... it was also more than $500... so it better be good...
Good stuff, Craig.
The primary limitation on the low frequency limit of gated SPL measurements is the distance to the nearest room boundary. The smaller the room, the higher the low frequency limit will be. Gated measurements in typical residential HT rooms usually are limited to 2-5 milliseconds, which means accurate response down to only 200-500 Hz. I wouldn't try to dig much deeper than that; it will be counterproductive and you will start to see room effects.
Yep, you'll need a 140 dB mic for the B4+.
Ed - Exactly... The ETF software is excellent for the upper ranges, and in our 43x16 foot room, the lowest limit is the 200 Hz... I have not even tried the below 200 Hz software yet, but it should be very close to TrueRTA..
Having it as really more of an addition to TrueRTA than a replacement because, in reality, the room WILL have an effect on a speaker... so seeing a TrueRTA raw graph and a "compensated" ETF graph will just give more information.
The ETF has been very useful in the measurments of the Ascend 170's, the Rocket ELT-Cse's, and the Axiom M22-ti's... All three, by the way, are great speakers for the $$$$
I've often thought one could test speakers out of doors. With the speaker (or sub) raised above a dense, broad hedge or even better an area of close-packed shrubs. I would imagine that the shrubbery would act as an efficient form of absorbtion for sound waves going down. Then absorb the reflected waves on the way back up again. Double the absorbtion for your money!
Crazy idea? What about a closely packed conifer forest using a cherry-picker or tower to lift the speaker above the vegetation? Wouldn't is make an even better absorber for the lower frequncies? Or would the sound still reflect off the ground beneath the vegetation?
Should I patent the poor man's anechoic chamber right now?
Chris - That was actually in the movie "Fred and Barney Go into Business" (AKA The Flintstones, Part V) ... They were able to get a response of +/- 4 dB from their 120 foot Brontosaurus powered subwoofer.... and used the "forest anechoic" chamber....
Craig and Ed:
what kind of rig should i get if i want to take in-room measurements of my sub (B4+) in an effort to get the most accurate idea of its response so i can then apply a little EQ'ing?
i wasn't aware that there were different mic's for indoor and outdoor measuring....