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Alpair 7P & Alpair 12PW combination.

Hello Dave:
Those cabinets look nice.
Although they are a little "boxy" looking. Are there ways to change the configuration a bit to make them a little more interesting or even pretty?
Bi-pole with the 12pw, more narrow face, vent to the back or bottom, rolled corners??? That kind of thing.
Where do you think they land respecting db/watt.
 
I thought that the drawings would be needed to determine what types of changes would be possible.There is often more going on inside than can be seen from the outside.
Thanks


having built this particular pair, and several other of Dave & Dr. Scott's designs, yes, reconfiguring to narrow / deep would change several things, but might make shoehorning the mid/tweet's TL between the woofers a bit simpler
 
break-in

Man, that sucks!

I mean, that is a tad impractical if you ask me. For others, it may become even more impractical. Consider people living in small apartments, or in a room/dorm. Leaving the system on 24/7 is bound to irritate people in such a situation, up to the point where the break in process may be a deal breaker for some. I sincerely think that a lot of (potential) buyers of the Alpair series would feel that an accelerated break-in procedure would be of great help. It may even advance sales a bit... Maybe achieving 100 % break in is not feasible/desirable, but say, 75% of the way with accelerated aging, and 25 % during normal use would be a good goal.

I am aware of the position of Mark Fenlon on this issue, but especially he is in a position where he will always have speakers to listen to, while his new creations are breaking in around the clock somewhere else, and so he has no reason to deviate from the process he considers best. But his optimum is not automatically someone else's optimum. I am not the kind of guy who takes "nope, can't be done" easily. But I also don't like to whine without contributing to a possible solution, so I'd like to think about the issue (perhaps in another thread), and offer up my pair of A7P's as guinea pigs, when a credible method comes out of the discussion. Does that sound reasonable/feasible?

Hi there T: Try it you'll like it. I have averaged 12hr a day for two weeks, rather than 24/7's. regards Michael
 
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Yesterday, they had over 240 hours of break-in on them when I turned the setup off. This weekend, I'll try them again. In the meantime, I have constructed an adapter ring for a different driver, so that the driver-with-ring physically drops into place of the A7P. With this "Frankenpair", I wanted to see if there are any common features in the response, in order to get an idea of the influence of the cabinet on the response. Up to about 3 kHz, the response wiggles are similar, and thus probably caused by cabinet diffraction alone, but above that, they "fly apart", probably caused by differences between the driver's response (both on- and off axis) and the slight different in cone size. To do: compare pre and post BI measurements and listen to the system using the same tracks as I used before.
 
It has taken me a while to get to it, but I have retried them. Their character hasn't changed as far as I can judge, and also the measurements don't show any difference in the bigger picture. There has been a subtle change at the point where the top-end resonance starts, but that's about it.

Compared to the Frankenpairs, they A7P's are more extended, but the Frankenpairs are much smoother in the 6-16 kHz region, and they gradually roll off over 16k. All in all, while they miss that little "sparkle" that the A7P's give, I find them more pleasant and easy to listen to.

A few words on the A12PW are in place here. It plays very nice with the Frankenpairs, and due to its extended response and gentle roll-off, arriving at a target response with a passive filter is a doddle. They are capable of significant bass output, so all in all I am quite satisfied with them. But it seems like they won't be used along with the A7P's.
 
I tried anywhere between 500 and 1000 Hz, first order electrical. I have a box with filter components that kept filling up slowly but steadily over the years, and it came in very handy. Because the baffle step frequency is a bit different for both drivers, I found a series filter didn't work well. Series filter forces the electrical response to always sum up to 1, and that's what this cabinet doesn't need.

I also have a nanoDigi (just got it a week ago), and with that I could try lower and higher frequencies and higher order filters. While the parametric EQ and freely programmable XO in the nanoDigo gives you quite a lot of space to tinker, no amount of processing can negate the influence of stored energy. It was funny to notice that each different driver would still keep quite a bit of its character, despite equalizing. The starting point therefore should (IMO) always be with drivers of which the "voice" suits your taste, rather than try to hammer a driver's response into a shape it was never meant to have.
 
Curious, given that the A12PW is a "bass-wide" driver, have you experimented by setting higher XO (>2k, >3k) and having a listen? I know it becomes a 2 way instead of a FAST, but since you have the drivers, might be worth a try? Also will give us a subjective impression on the bass-wide capabilities of the Alp 12PW.

p.s. I am making the assumption that you have tweeters in your parts bin... :)
 
Yes, I have some tweeters in my bin, and trying them is on my agenda. But I don't expect optimal results from them, because the low intended crossover point allows a bit more space between the drivers, and I have used this leeway in order to keep both the woofer and tweeter a couple of centimeters away from the dividing panel between both drivers' volumes. So vertical lobing will be somewhat more pronounced with a higher crossover point.

In the meantime, I am totally confident that the A12PW will be easy to integrate with many tweeters. Not only is the response extended, but the dropoff starts out gently, and it gradually steepens as frequency increases. Minimum phase behaves well up to 10 kHz before it starts to veer off. Such a response is rather easy to forge into the target shape without having to resort to hideously complex crossovers. For example, it is quite easy to achieve a low pass rolloff that resembles a 1st order acoustic response from between 500 and 1000 Hz and up to about 10 kHz, using just a coil and a resistor. Not a lot of drivers can do this. Bass output is ample and sufficiently low for music when fed with about 40 Watts (I wouldn't go much higher with them). For home theater sound FX, they will probably not do, but this should come as no surprise. They were never intended for such use.

My only little gripe with them is the dip in the FR around 500 Hz, accompanied with a blip in the THD at this frequency. But it probably only bothers me because I know it is there, and it is best left uncorrected. I tried correcting it (digitally), resulting in a flat response around 500 Hz, but the cure was far worse than the problem soundwise. Their overall sound is friendly to the ear, and when used full-range, they sound a bit laid back and dull due to the lack of treble, but that's it. No nasties whatsoever.
 
Thanks timpert for your detailed response.

You have confirmed my suspicion that the potential of using this driver for 2 ways with simple XO has been largely overlooked (if I may me say so, specially by the manufacturer); with such extended response, crossing low with these drivers feels like a waste.
 
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It may feel like a waste, but it's not. For example, an acoustical LR2 response using passive filter parts requires the woofer to have a malleable response (gentle rolloff) or a response that extends flat to at least four times the intended crossover frequency. The A12PW gives you both. Also, if the usable frequency responses of woofer and tweeter have a large overlap, you can opt for a first-order acoustical crossover slope in that range, giving you a step response that few speakers are capable of.
 
Was reading in another thread the the step response is an important factor in "good sound". Thanks for the explanation - will keep in mind when I get into 2 way projects.

Btw, going a bit OT - the link below will take you to details of Mark Audio's earlier woofer - more budget priced and not with the same wide-band response as the A12PW:

http://www.creativesound.ca/pdf/EL166-data-100610.pdf

Few folks have done decent builds with those, including P10 - their earlier MTM FAST was based on the EL166.
 
I found this Thread while searching for information on the Mark Audio 12P/7 combination. I was disturbed once again by the latest iteration of "Mr. Know-nothing", who proceeded to challenge a true expert in their field.

I want to thank Mr. Fenlon pointing out what kills my enthusiasm for every audio forum, the tolerance of the anonymous know-nothing bully. Tolerance of obvious idiots almost ruined this very interesting thread. I never would have seen the 'Build' that resulted, and been inspired to consider it, had it not been for Mr. Fenlon calling this fool on the carpet. Thanks again.
 
I found this Thread while searching for information on the Mark Audio 12P/7 combination. I was disturbed once again by the latest iteration of "Mr. Know-nothing", who proceeded to challenge a true expert in their field.

I want to thank Mr. Fenlon pointing out what kills my enthusiasm for every audio forum, the tolerance of the anonymous know-nothing bully. Tolerance of obvious idiots almost ruined this very interesting thread. I never would have seen the 'Build' that resulted, and been inspired to consider it, had it not been for Mr. Fenlon calling this fool on the carpet. Thanks again.

Just noticed we seem to have lost Scottmoose too. What a pity.