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-   -   alpair 10 box width ? (http://www.diyaudio.com/forums/full-range/144069-alpair-10-box-width.html)

norman bates 13th May 2009 07:45 PM

alpair 10 box width ?
 
Seeing the lift in the lows, what would be a good box width ?

http://markaudio.com/sites/all/files...Full-Guide.pdf

I'm thinking a theoretical baffle step -3db near 400hz..........

Maybe 11" wide box ?


Norman

CSS/XBL 13th May 2009 08:03 PM

Hi,

Carolina Audio's design is 13.5".

http://carolinaaudio.com/KOTA/Page_5.html

Bob

norman bates 13th May 2009 08:22 PM

wow, I didn't know they switched over to the alpair................

$1,200 (if that is the introductory price for a pair) seems fair...


Norman

Henkjan 14th May 2009 02:35 PM

Jim's design is 7.5 W and uses no BSC either..

http://www.diyaudio.com/forums/showt...585&highlight=

Jim Griffin 14th May 2009 03:09 PM

Baffle Step Comp
 
Yes, my speakers are 7.5 inches wide.

Lately, I have been listening with a little BSC. I use the classic R-L network--a 1.5 mH coil with a parallel 2 ohms resistor--in series with one of the terminals to each speaker.

You can change the resistor to suit your taste from 2 to 8 ohms. For me the 2 ohms value with the coil sounds better than no BSC network. My rear ported speakers are 18 inches away from the rear wall so I do have some acoustical support from that surface.

Jim

norman bates 14th May 2009 07:16 PM

ah, thanks jim, henkjan, and css/xbl.

seems even against a wall, non boosting bass spkrs (unlike the alpair 10) usually need 2-3db of boost.

At most full range driver fans' volumes, I'd imagine people need more than 6db to make up for the fletcher munson curve.



Norman

Jim Griffin 14th May 2009 08:05 PM

Norman,

Baffle step compensation has nothing to do with the F-M curves. BSC is intended to adapt for the difference in the SPL level because of the transition from 4 pi to 2 pi radiation effects. Effectively, we are talking about up to a 6 dB in bass to mid-bass output levels unless the baffle step effect is addressed. Room placement and such contribute to the amount of compensation that needs to be corrected. Various methods can deal with the impact of baffle step but the insertion of the R-L network is effective for most situations.

Bottom line is that it has nothing ot do with the F-M curves which are the relative sensitivity of the ear vs. SPL level and frequency.

Jim

norman bates 14th May 2009 11:18 PM

Hmm........................

well, at greater than 100db at listening spot, I needed zero baffle step............... but listening at 70db it is drastically needed.

I bet that to one's ears, the smily face curve on an equalizer settings sound better at low volumes. Then when cranking it, turning it back to flatter would sound better. Some older receivers had a loudness knob that varied the amount of boost based on volume setting.


I added a second 15" (to a 15") as a baffle step woofer with a pole near 200-300hz @ 6db(big rig setup). At 70-80db you couldn't even tell when the baffle step 15" was hooked up or not sitting 2' from it touching the speaker wire to the inductor. Once you started laying the wood into it, adding the .5 woofer really made a difference on drums.


So regardless if 1 is related to the other...........

Most of our skinny speakers require have baffle step, then boost them even more and they will sound better.

I say you dial in the baffle step close to usual volume settings.
And more boost down low sounds better for <90db volume levels.
I think bob Brines does that with his mltl 167e, but I could be wrong.



Norman

Jim Griffin 15th May 2009 12:28 AM

Norman,

You have both feet in the sand box.

I suspect that what you hear is caused by compression within the driver and not a manifestation accountable to the F-M effect. Unless Bob Brines has a feedback circuit within his speakers, there is not a way to vary the compensation in a dynamic fashion without involving electronics beyond the loudspeaker.

The best suggestion that I have is to work out the BSC for the normal listening level and allow higher level compression effects go as they may.

Yes, older receivers and preamps had loudness circuits to boost bass output at low levels and reduce them as loudness increased. Unfortunately, most current preamps don't give you that option.

Jim

norman bates 15th May 2009 03:54 AM

I'm sorry, I was not clear...............

I did not mean to say that Bob's passive bsc filter changes based on volume level.

"You have both feet in the sand box."

I'm not sure what you are trying to say, but thank you if it was a compliment, and double back to you.

The f-m curve and baffle step are very important to us full range driver people that listen at medium to low volume and have narrow enclosures.

I see the 2 issues as one lumped problem that can be solved by using a baffle step filter that is more than 6db. The highs will be less attenuated by the bsc circuit because the impedance shoots up in the high end assuming there is not a zobel filter.

Voila, we have replicated what a simple 10 band equalizer (using a smily face setting) can do for us.

Norman


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