Twin Alpair 7's studio monitor build. - Page 2 - diyAudio
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Old 28th February 2014, 01:09 AM   #11
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Originally Posted by nirvana View Post
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.

Click the image to open in full size.

dave
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Old 28th February 2014, 01:11 AM   #12
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Originally Posted by xrk971 View Post
Putting a cap across the lower driver to turn it into a 1.5 way
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
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Old 28th February 2014, 01:14 AM   #13
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Click the image to open in full size.

dave
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Old 28th February 2014, 06:05 AM   #14
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oh, is that a case of built it, and they will come?
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Old 28th February 2014, 06:18 AM   #15
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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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Old 28th February 2014, 11:41 AM   #16
xrk971 is offline xrk971  United States
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Originally Posted by planet10 View Post
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.

Last edited by xrk971; 28th February 2014 at 12:00 PM.
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Old 28th February 2014, 02:32 PM   #17
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Originally Posted by xrk971 View Post
... 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).

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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.

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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.

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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.

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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.

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...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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Last edited by Scottmoose; 28th February 2014 at 02:44 PM.
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Old 28th February 2014, 03:19 PM   #18
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Originally Posted by lorienblack View Post
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.
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Old 28th February 2014, 06:54 PM   #19
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Originally Posted by lorienblack View Post

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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Old 28th February 2014, 07:07 PM   #20
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I've warned you about the moonshine before Chris.

Yep, bespoke. It's not the same as the obsolete one for the original A7.
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