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
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
Thanks,
John
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
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.
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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
I am using an 8th order high pass. Are you using something that is at least this sharp?
Bob
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
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
Well, you can only tell so much from FR plots. Not having an anechoic chamber, the bottom end on my plots either are theoretical or show what the room sounds like. Since the top end should pretty much reflect what the driver sounds like, you can gain all you need to know from the manufacturer's plot. I realize that in this case, Mark has not published the 15* and 30* plots for the A12P. You will have to trust me on this: There is little or no difference between the dispersion of the A10P and the A12P. You should make your decision based on whether you want the slightly better detail of the A10P or the better weight of the A12P. It really depends on the music you will be playing most of the time.
Bob
Bob
Yeah... I ran both drivers through Martin King's MathCad programs the other day. I put each driver in an MLTL and optimized it to the best of my ability. Here's what I found:
* The A10P can produce bass down to the high 30ies Hz. The A12P likes the low 40ies better. Yep, that's right. The bigger driver results in a higher f3 in my sims.
* The A10P produces 97 dB SPL at 5 W input. This is the power where it hits Xmax at 30 Hz. The A12P produces 100 dB SPL at 7 W input. This is the power where Xmax is reached at 30 Hz. The difference between 5 W and 7 W is 3 dB. In terms of perceived loudness, that's actually a pretty small difference. I just grabbed 30 Hz out of ... the blue.
* Cone break-up in the A10P starts around 3~4 kHz. For the A12P, it starts around 1.5 kHz. Kudos to Mark for taming the breakup. This is physics at work. But it does provide a possible explanation for why the A10P is reported to sound more detailed.
So basically, my conclusion is that $50 per driver buys you higher sensitivity. If that's your priority, get the A12P.
In my case, however, I prefer detail over bass punch, so I think I'll go with the A10P. I do know I prefer paper/fiber over the metal cones.
I think I've gone as far as I can in terms of reading up on the drivers and simulating their performance. To find out for sure if I like them, I have to actually build some speakers. Ya' know... Get my butt off the internetz and into the woodshop/garage...
Thanks Bob (et al). I appreciate your inputs.
~Tom
* The A10P can produce bass down to the high 30ies Hz. The A12P likes the low 40ies better. Yep, that's right. The bigger driver results in a higher f3 in my sims.
* The A10P produces 97 dB SPL at 5 W input. This is the power where it hits Xmax at 30 Hz. The A12P produces 100 dB SPL at 7 W input. This is the power where Xmax is reached at 30 Hz. The difference between 5 W and 7 W is 3 dB. In terms of perceived loudness, that's actually a pretty small difference. I just grabbed 30 Hz out of ... the blue.
* Cone break-up in the A10P starts around 3~4 kHz. For the A12P, it starts around 1.5 kHz. Kudos to Mark for taming the breakup. This is physics at work. But it does provide a possible explanation for why the A10P is reported to sound more detailed.
So basically, my conclusion is that $50 per driver buys you higher sensitivity. If that's your priority, get the A12P.
In my case, however, I prefer detail over bass punch, so I think I'll go with the A10P. I do know I prefer paper/fiber over the metal cones.
I think I've gone as far as I can in terms of reading up on the drivers and simulating their performance. To find out for sure if I like them, I have to actually build some speakers. Ya' know... Get my butt off the internetz and into the woodshop/garage...
Thanks Bob (et al). I appreciate your inputs.
~Tom
actually, to be anal about it, I think Mark has designated the 10P as Gen 1 (current version that is - even those lucky enough to chat with him regularly could be surprised with what Team Alpair has going on in the group-think tank
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