Twin Alpair 7's studio monitor build.

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I've just put these together and thought I would share some pics and initial impressions.

I'm delighted :) the imaging and soundstage is exceptional, as is the detail. I am hearing things that escaped my ear with my 10.3 pensils, it's almost as if I can hear the instruments as well as the sound they make. If that makes any sense at all. With about 100h on these drivers I am expecting even more delights, as I was blessed with as my 10's continue to improve.

Heart felt thanks to the mighty Moose for the design and support, your a star.
 

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Lorien,

Good to see that you've completed the build, and the results are sweet! :) I however am not too surprised as a Dr. Moose design featuring Mark Fenlon's Alpair 7.3 is not likely to disappoint. Enjoy!

Keep us posted on the progress as you rack up more hours on the drivers. Btw once the drivers have ~200 hours, it might be worth running the bottom driver as a 0.5 driver and see if there is a noticeable difference.

- Zia
 
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Thanks, I will do that. Is there a tried and tested line level crossover design to impliment this?

Will also try to get some more pics up, it's tough from mobile devices sometimes.

God darn these are lovely, maybe too delicious for studio monitors :)

I've just put these together and thought I would share some pics and initial impressions.

I'm delighted :) the imaging and soundstage is exceptional, as is the detail. I am hearing things that escaped my ear with my 10.3 pensils, it's almost as if I can hear the instruments as well as the sound they make. If that makes any sense at all. With about 100h on these drivers I am expecting even more delights, as I was blessed with as my 10's continue to improve.

Heart felt thanks to the mighty Moose for the design and support, your a star.
 

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Update - monitors are running with cap across lower driver, 70uf, improved overal coherence and imaging.

Had their debut in London studio today! unanimous consensus - ultimate winner against Genelec, ATC and the dynaudio. Still some burning in time and tweeking to do, but an amazing result.

Hats off to Mark and Scott.
 
Lorien-

Can you guesstimate efficiency? I've been drooling over MA drivers for a while for use with a SET but I fear the wife's wrath if I try to stick a 10/12 Pensil in the living room. The slim 7 Pensils would probably be welcome, but I worry about lacking volume with only 5W on tap. Twin 7's seem like the proverbial porridge with the slim looks of but higher efficiency than singles.

Beautiful build, by the way!
 
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Looks very nice and good to hear that it did well in listening tests against real monitors in the studio. A studio monitor's main call to duty is having a flat linear response. Do you have any measurements yet? Putting a cap across the lower driver to turn it into a 1.5 way is kind of an underutilization of a nice full range driver as you have turned it into a woofer that is probably crossed below 500 Hz? Curious how deep the bass extension goes with the dual chamber reflex.
 
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twin Alpair 10p .....is this possible ?

Sure. 1 driver will likely need to be rolled off or the cabinet a bit exotic. Cogitechis currently building a castle-style microTower derivative with A10p and A10.2, no reason a variation for A10p couldn't be done.

The attached are the extents of a Twin Mar-Ken10.2T, i haven't yet detailed the small changes, but it will work with A10p as well. Colin built the earlier rectangular one for the original A10.

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dave
 

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XRK971 - the monitors have been left at the studio for a couple of guys to try mixing with, another important test. I have requested that the tech man does some measurements for me, so I hope to be able to post some results soonish.

The Bass is awesome considering the size of the drivers, but you need a bass rich track for it to overcome the very lively upper mids and top. I have a feeling that the tonal balance will even up some with a little bit more run in.

That said, the bass was noted to be more natural and defined in comparison to some of the other monitors with larger cones and higher power ratings.

ALL of the other monitors sounded sluggish and muffled by comparison when we switched between them, sort of drunk.

Build them and they will come? Sure hope so, between degrees and fatherhood I've forgotten what disposable income feels like ;)
 
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But not as usually thot. A cap across oneof the A7s means they are wiredin series, unless you are running a current amp you do not get any gain in sensitivity, but you do get 2x the conearea and a reuction in excursion by a factor of 4.

dave

Putting the drivers in series with a 70uF cap across the bottom one effectively makes it a low pass filter that rolls off at 6 dB/decade above 2kHz. This is why I was saying it is kind of a waste to use an A7.3, renowned for its high frequency ability as a woofer in a 1.5 way speaker. The 70 uF is still not large enough to pull the frequency below the comb-frequency limit defined by the center-to-center spacing of the drivers which is well below 1 kHz. Also, putting the drivers in series makes the speaker an effective 16 ohm load below 2kHz - which will not be good from standpoint of getting enough power to the speaker using conventional 8 ohm rated amps with limited drive voltage.
 
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... A studio monitor's main call to duty is having a flat linear response.

Not so. That is certainly required of one variety of studio monitor, but, to give two examples, tell that to the BBC, who regularly response shaped their monitoring speakers depending on the task they were expecting them to be used for, or the Yamaha NS10, which is also far from flat. The latter, incidentally, has a dodgy reputation in some circles, largely IMO because it's misused. Monitors are like anything else -they vary with requirements. Nor is there supposed to be a fixed use for these things (as far as I know anyway) -the name simply got hung on them, largely because they're partly inspired by an old box for the 1st Gen. unit I did which also had that name (not one I gave it).

Putting a cap across the lower driver to turn it into a 1.5 way is kind of an underutilization of a nice full range driver as you have turned it into a woofer that is probably crossed below 500 Hz?

In your opinion perhaps. But it's far from being a waste. Recall that you have consistency of frequency, impulse & inherent phase responses by using the same unit, and they are acoustically akin, thus there is no mismatch & you have much greater flexibility in terms of low-pass frequency and slopes, plus the option not to run one at all if desired.

Putting the drivers in series with a 70uF cap across the bottom one effectively makes it a low pass filter that rolls off at 6 dB/decade above 2kHz.

Yes. I designed it, so I'm aware of what it does.

The 70 uF is still not large enough to pull the frequency below the comb-frequency limit defined by the center-to-center spacing of the drivers which is well below 1 kHz.

Who said that is a limit and that the skies will automatically fall in? It depends what you are doing and the circumstances: this is not a cast-in-stone point on the one side of which terrible things occur & on the other, all are sunlit uplands of peace and prosperity. Very simplistic paper categorisations of that kind are just that: very simplistic and do not account for a host of real-world factors which need to be considered. To the best of my knowledge you've been running twin Vifas in various designs on & off for long enough to have appreciated this.

Also, putting the drivers in series makes the speaker an effective 16 ohm load below 2kHz...

Not so. Re on the 7.3 is 5.4ohms. < 2KHz it's hovering around the 6ohm area.

...which will not be good from standpoint of getting enough power to the speaker using conventional 8 ohm rated amps with limited drive voltage.

Most are perfectly capable of driving them.

X -no offense, but could you please remember I might actually know what I'm doing, and even possibly have considered the things you mention?
 
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Update - monitors are running with cap across lower driver, 70uf, improved overal coherence and imaging.

Had their debut in London studio today! unanimous consensus - ultimate winner against Genelec, ATC and the dynaudio. Still some burning in time and tweeking to do, but an amazing result.

Excellent! :) Really glad they went down well. All of the speakers mentioned are going to be voiced differently & have different traits, but the fact that thus far they were liked by presumably experienced listeners who know what they want from a speaker is nice.

Re sensitivity, it will remain per a single 7.3, but n0 for the system is doubled for the same input, so as Dave notes, you've got double the cone area & power handling, and significantly reduced individual deflection, so distortion also drops.
 
Build them and they will come? Sure hope so, between degrees and fatherhood I've forgotten what disposable income feels like ;)


note from the time stamp on the post, this was a late night scatological response to sodacose's preceding reference to his sig line

ethyl and late night posting - you'd think I'd have learned better by now ;)

sorry if I've missed it before, but was this particular design bespoke, or has it been publicly posted?


edit: never mind, found it
 
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