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Old 25th April 2013, 02:04 PM   #21
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Quote:
Originally Posted by silverhairbp View Post
Bob, have you tried any acoustic insulation besides fiberglass? I've noticed different results from the denim material and the poly-based loose fill.
At the moment, the speakers have 5/8" of fiberglass on the back wall and fairly heavy polyfill behind the driver. I am going to increase the thickness of the fiberglass to see if this is indeed the problem. Fiberglass is very effective at the frequency of interest.

Bob
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Old 25th April 2013, 05:11 PM   #22
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Bob Brines View Post
At the moment, the speakers have 5/8" of fiberglass on the back wall and fairly heavy polyfill behind the driver. I am going to increase the thickness of the fiberglass to see if this is indeed the problem. Fiberglass is very effective at the frequency of interest.

Bob

any lining on at least one of the side walls?
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Old 25th April 2013, 05:49 PM   #23
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The entire cabinet is lined with 5/8 fiberglass. Top but not bottom. The cabinet has ~3/4lb polyfill in the upper 30", bottom 10" empty. I don't usually pack a cabinet like this, but this one needed it to kill the 5th harmonic.

Bob
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Old 16th June 2013, 02:14 PM   #24
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Hi Bob and all interested in this design. As I prepare to build this one, I am wondering if there are any changes regarding dimensions, bracing, stuffing, lining, etc. I ask here on the forum so that anyone who has bought the plans from you can benefit from the answer instead of you having to reply to multiple emails. My own 12P's have probably 1000 hours on them in hastily built pensil with no bracing. They good but in my search for more bass I am willing to try as many ideas as possible.
Thanks,
John
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Old 16th June 2013, 05:04 PM   #25
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You are not going to get a lot of bass out of the A12P's. It's there, its comfortable, but it is not chest thumping. I find that my M12-A12's really do need some BSC. My solution is to apply some EQ - bass boost - through my music player. At 70-80dB @ 2.5m, the A12P's can stand quite a bit of bass boost without exceeding Xmax. I also apply a brick wall high pass @ 30Hz just to protect the drivers from any loud and really low content.

I have not changed anything in the plans. I recommend the fiberglass lining as a necessary first step, then voice the speakers with the stuffing of your choice. As with all of my speakers, the bottom is open so that stuffing can be adjusted.

Anyone who purchased the plans: If the plans you have do not have 5 pages including the grill, send me an email and I will get the latest revision to you.

Bob
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Old 16th June 2013, 07:35 PM   #26
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Sounds good. I am using th preamp of my Yamaha HT receiver so I can do a max 10dB bass boost into my 300b mono blocks. Works good with the 7.3 pencils!

John
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Old 17th June 2013, 01:30 PM   #27
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Quote:
Originally Posted by Bob Brines View Post
You are not going to get a lot of bass out of the A12P's. It's there, its comfortable, but it is not chest thumping. I find that my M12-A12's really do need some BSC. My solution is to apply some EQ - bass boost - through my music player. At 70-80dB @ 2.5m, the A12P's can stand quite a bit of bass boost without exceeding Xmax. I also apply a brick wall high pass @ 30Hz just to protect the drivers from any loud and really low content.

I have not changed anything in the plans. I recommend the fiberglass lining as a necessary first step, then voice the speakers with the stuffing of your choice. As with all of my speakers, the bottom is open so that stuffing can be adjusted.

Anyone who purchased the plans: If the plans you have do not have 5 pages including the grill, send me an email and I will get the latest revision to you.

Bob
you have a brinckwall eq at 30hz? Even in my standmount BR alpairs 12p, when I tried to apply eq at 25hz, I heard it? Is it my brain or what? when I eq at 30hz, I definitely hear it so I dont put any.

I gotta say, im definitely impress by the bass those alpair delivers. I'll take the measurments this week, but damn I didnt thought I would have satisfying bass down to 40hz: ita not flat down there, but its there enough so that I hear the presence.

Last edited by murphythecat8; 17th June 2013 at 01:37 PM.
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Old 17th June 2013, 02:15 PM   #28
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I suppose that it depends on what you are listening to. With most classical music the only sounds below 30Hz are the sounds of the hall -- the HVAC plant, the nearby subway. Yes, I forgo 32' organ stops, but I can live with that. Call in the sub.

I am using an 8th order high pass. Are you using something that is at least this sharp?

Bob
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Old 22nd October 2013, 05:01 PM   #29
tomchr is offline tomchr  United States
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Hey Bob... Do you happen to have directivity measurements on your M12-A12? I'm curious to see how it stacks up against the M10-A10.

Thanks,

~Tom
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Old 22nd October 2013, 05:48 PM   #30
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Actually not that I am willing to share. I was having problems with my equipment that day and I had a lot of ripples in the traces that were not real.

Suffice it to say that somewhere around 15* the trace is pretty much flat to 13k then spikes at 15k and then dies around 20k. The trace looks a lot like the A10p 15* trace except it is hotter around 15k.

Bob
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