Alpair12P gen2 stand-mount speakers

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Toppsy
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#1 Alpair12P gen2 stand-mount speakers

Post by Toppsy »

At last I managed to find the time to build these speakers.

They are a small vented standmount, ported from the rear to help with some bass boost from rear wall. The initial design is that of Scott Lindgren, (Scottmoose to you all on this forum) and drafted by myself with some small modifications. Scott did say the bass from these would perhaps not be as low as some the other MA drivers so with this in mind I decided to place the port on the rear to allow for corner or back wall loading.

The elegant curved stands were an inspiration from a design I saw at a local DIY meet some time ago of a small infinite baffle stand-mount pair of speakers using the Alpair10 drivers and designed by Ed Swift. The end result I'm quite pleased with. I think in this case its more "imitation being the sincerest form of flattery". I do hope our Ed doesn't sue me for copyright

Initially I placed the speakers pushed back into the alcoves either side of my fireplace. The drivers are still not yet fully run in however; initial listening impressions are very favourable. These drivers are very revealing with great soundstage. As Scott did mention bass is not the lowest I have heard from other MA drivers (the smaller A10 producing more bass clout) but this is not what the A12P is all about and the rest of the music reproduction more than makes up for this. However having said that the bass is very respectful indeed and can improve when the drivers are fully run-in and the cabinets have settled down and are position up against a flat wall.

Later I hooked them up to my SE300b monobloc amps with the speakers placed about 150mm off a straight wall. In fact they were placed either side a 1.2m long fish tank sitting on to a 1.5m long furniture sideboard. Not the most ideal position but it allows them to fire down my 5m long listening room. They sound really good indeed in that position and from such a small(ish) speaker one couldn't grumble at all of the bass these are producing. It is clear and concise though perhaps missing the bottom octave but this doesn't detract from the engaging listen. With a SE valve amp these are simply wonderful and involving to listen to. The micro-dynamics is superb and though the sound-stage not the best I have heard the singer is never-the-less projected well forward in the mix. Mark has produced a really good driver in the A12P, my hats off to the designer.

Out of interest I had a play with different amps with these speakers. My SE300b monoblocs, my 6EM7 integrated and a PassLabs F5 that I have on loan from NickG.

The interesting thing with this experiment was the different portrayal of the soundstage. The tube amps outperformed the SS amp even though all 3 amps share the same basic unity gain pre with Silk TVA's. So the only conclusion I can come to is these drivers excel with a tube amp so will be a good driver for those on this forum.

I'm reet chuffed with these simple BR speakers.


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chris661
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#2

Post by chris661 »

Hi Colin,

I wonder if the soundstage could be improved by rounding over those edges?
I like the looks of these - they seem very compact given the driver size - Decent WAF, I expect.


When Dad's back from Malaysia, methinks a listening sesh is in order, anyway.
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#3

Post by Toppsy »

Hi Chris,

I reckon a listening sesh a good idea.

I had thought about rounding-over all the edges of these, not for any sound improvement possible gains but with a view to having them spray painted in a colour similar to the cones. Spray painted speakers and sharp edges don't go for a perfect edge finish!

However, after some feedback on the Diyaudio forum pages the consensus is for a real wood finish so I have ordered some rather nice Birch Burr to cover these. So rounded-over edges are a no no I'm afraid. Suppose I could consider my signature build 45-deg chamfer to the front baffle.

I originally had these drivers mounted in some open backed mdf boxes of similar proportions and baffle size and did this experiment of those. To be honest I could not detect any difference in soundstage presentation without and then with the rounded-over edges. I think it's just a trait of these drivers, but having said that the soundstage is as good as most the Fostex of similar size I've heard but not quite as good as say the smaller MA A7.3.

See what you think when you and dad come over. But I reckon for such a small and simple a design that is so quick and easy to build these are really very good. Bear in mind these drivers are not designed for the likes of rock or heavy metal type genre of music and focus on micro dynamics voice and subtleties in the music mix. In that sense these boxes deliver.
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#4

Post by Andrew »

They look amazing Colin, another winner! Should be good in an exotic burr veneer...another Topps job.
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#5

Post by Mike H »

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#6

Post by Toppsy »

Yesterday I decided to fix the spikes to the pedestal stand base and bolt the stand to the speakers. I used M6x10mm threaded inserts drilled into the speaker base and M6 roofing bolts with 20mm dia washers to fix speakers to stand. To hide the fixings, I inset the washers and bolt heads into the top shelf of the stands.

This has tightened up the whole sound and improved imaging. They are now sitting happily either side the fireplace with the rear ports firing into the alcoves either side the chimney breast. This was a well worth exercise. :D

I normally would shy away from burr veneers and recommend if anyone wants this type veneer to have it done profesionally. However, I'm assured the veneer I shall be using (Birch Burr) is nice and flat and quire easy to work with, so I thought I'd have a go on these small cabinets. Here's a photo the actual veneer:

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I originally enquired and got quotes for this a couple months back for a pair of Edingdale speakers but the guy ended up choosing American Black Walnut. I won't know until tomorrow if they have any left but I only require a single leaf as the isze of the leaves is 237cm x 70cm but I've ordered 1 leaves to be safe I have enough for the stands as well.
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#7

Post by Andrew »

Just listening to these at Colin's - my cunning plan is to get up really early in the morning and steal them while he's still asleep!

Seriously, tho they are the closest thing I have heard to Quad63 but without the 2 ohm load hassle, they have amazing speed and focus; I like these a lot, they suit my tastes and work nicely with 300B power.

Its like having a pair of headphones but in the room.

We plan to compare them to his Rossendale floorstanders later, I'll get a idea if they lack bass then, but right now I could be convinced that they don't, its so tight and fast, perhaps a little recessed. Colin has them running with just a touch of T90A super tweeter, through a very small cap, the effect is very subtle but just takes off some of the driver's inherent dryness.

I'm curious as to how they will perform in the Pencil design.

In terms of a 2-way, the challenge will be finding a suitable bass driver to match these lightening fast drivers, stunning.

His choice of veneer? Well let just say, the photo doesn't do it justice...

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#8

Post by Andrew »

I got up early but didn't have the heart to steal away with them, I must admit I was tempted, they are that good. But I could never do that to Colin....

Two things penetrated my thoughts last night, one is that if you view these as mini monitors they really are fabulous, sure they don't go mega low but, as monitors they are the best I have heard.

We played several tunes last night many new to me, of the ones I did know the only time I noticed the lack of bass was Metallica S&M torture tracks, they sounded great but the Sachiko's make your hair stand on end, while these just sounded very good.

The other was that some bass support really would move these speakers to a different league, but finding a bass driver to match to these Alpair 12's will be a real challenge for Colin and Scott.
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Paul Barker
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#9

Post by Paul Barker »

This is very interesting. Would they go well with a bass helper in the same floor stander, but instead of the usual two driver arrangement of mid/bass : tweeter use full range : low bass, just like we do with the OB's but having the supported bass of box design, whichever of the many method's that may be.
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#10

Post by Cressy Snr »

Sounds like another winner there chaps.
What we need is a couple of pictures so we can appreciate the burr veneers.

What I have always liked about small loudspeakers, is their image creating attributes. The lack of bass becomes secondary when you have such reach out and touch realism.

I can see these doing very well with as you say some kind of bass reinforcement setup. Active subs are one solution to that problem, the cost of getting a few in to try would be a stumbling block but IMHO could be one way forward in the LF department.

OTOH a commercial class D plate amp and a few experimental boxes is another way to experiment with bass reinforcement, but again we run into the cost of buying drivers. I think sealed box bass in a hefty birch ply/MDF sandwich enclosure and a big plate amp to provide the speed, control and drive, would suit these speakers. This then leads to the possibility of isobaric loading. I would steer well clear of ported bass reinforcement unless you actually want to turn your system into a lead booted boom box :wink:
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#11

Post by Toppsy »

The idea for a speaker for AndrewL is to do a floorstander with bass helper(s). I believe Andrew wants to run them as a 2-way with passive XO and to run with his 300b SE amps. So Plate amps and active subs are a no-no. Scott and I shall be considering several design options using perhaps 2 x 8" bass units either wired in series or isobaric. I am of the opinion we should keep the A12P's in their own space as also the bass units. The issue with the bass units, as Andrew has mentioned, is finding one that will keep pace with the FR drivers. However, I believe Scott may have a driver or two in mind. The idea is to design a speaker that takes up no more space than these standmounts but in a floor standing box.

I know Andrew is concerned that by adding some bass support to the MA drivers this does not take any of the magic from these. Hence the woofers will be XO'd at a low a frequency Scott feels practical.

I'll start a new thread when the design/build prototypes get underway.

SteveTheShadow wrote
What we need is a couple of pictures so we can appreciate the burr veneers.
So not the best of photos but here's a close-up shot of the actual veneer. The photo does not do justice to the veneer and the colour in real life is a little richer. I should mention this veneer, which is radial saw cut Birch Burr, comes in 237cm x 70cm leaves and costs £35/m². It is very flexible and flat. I don't expect any problems with this veneer. Finish shall be a satin acrylic varnish.

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#12

Post by chris661 »

Doing a passive (speaker-level) crossover at low frequencies will be difficult:

- the components required will be large (and therefore expensive if high quality ones are to be used)
- the impedance peaks from cabinet/driver resonance will create interesting results when they interact with the crossover

The only way to counteract the latter is to put the FR driver in a true TL, which would flatten the impedance peak.

I can bring my system around (that now has the drivers integrated properly, and works on the principle discussed here), and try using my woofers but with the Alpairs driven from some nice glowy valve amps.

Of course, being subwoofer drivers, they might not have the same sound as a midbass, it'd be free to try.
If you have any Edingdales left, we could feed them some LF using my active crossover and see how the Mark Audio midbasses sound in comparison.

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#13

Post by Toppsy »

Chris,
Scott and I are well aware of the challenges such a passive design entails and the challenge will be finding a right sized woofer (likely 2 per speaker) with high enough efficiency, speed, and Re to give a friendly amp load. They will also need to work in a relatively small enclosure so I suspect an infinite baffle box for the woofers, but maybe Scott has other ideas in the pipeline. I'm sure Scott has something in mind as he did ask me to clarify what budget constraints Andrew is working to.

I don't think cost is such an issue, as to the overall sound. Bear in mind these Alpair12P drivers cost around £350 a pair. Then factor in the cost of a pair of T90A supertweetrs - another £400 say. Suitable woofers aren't going to be cheap and remember Andrew wants to run the speakers from a single 300b SE amp.
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#14

Post by Andrew »

Although an active set up isn't what I'm after I am interested in hearing Chris's thoughts on these speakers and how they go with his little bass speakers.

Thinking on from Paul's idea I wonder how well a series crossover like we do in the OB's would work? We're pretty good at building them, after all.

I reckon this would make a nice OB driver too, though its the small-ish box size speaker I'm really after. I'm not sure these need an OB, tho they will be very good in one. On that note, in these small boxes, try as I might on Saturday, I couldn't hear any box sound.

In some ways I'm not panicking too much if Colin and Scott don't come up with anything, although I'm sure they will, as long as you are willing to accept the limitations of these speakers, as 'monitors', well what I'm saying is I reckon I could live with them even like that...I was thinking on the way home that they were like having a pair of earphones on but in the room.

There's always the MLTL 'Pencil' designs Scott has for these drivers.
Last edited by Andrew on Mon Aug 20, 2012 2:09 pm, edited 1 time in total.
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#15

Post by chris661 »

It'll be September before I can make it over there - the coast-to-coast ride is fast approaching, and then I'm on holiday after that.

I was thinking of only using the low pass output from the Behringer (to keep the signal path as best as possible for the Alpairs) to feed my woofers, and see how things go from there, just filling in what the Alpairs can't quite manage in the low end.

Here's a thought.
Does your 300B amplifier have a 4ohm output tap?
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