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Old 30th October 2012, 11:47 PM   #321
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by ParsonL View Post
This has been a helpful thread. I have been wanting to acquire a pair of AN15s and do something with them, but have struggled to know the best enclosure to utilize for such a large driver.

This thread, along with advice from Planet10, has directed me toward the boffle enclosure.

Bigun - are you satisfied with the bass output with the open back, and can you comment on the listening comparison (not merely the measurements) between open back and the closed vented enclosure. Thanks.
I've been so distracted with other things that I haven't tried it with the back on yet. I have a lot of business travel at the present time and don't expect to get around to more experiments until late December.

I am happy with the quantity of bass output from the open back but the quality of it isn't quite right - it's a little spongy and the freq response doesn't sound flat. However, this doesn't concern me, I don't think it's a fault of the driver or my future plans for this enclosure. I think it's mostly a limitation of this particular tube amplifier along with poor room positioning and the wrong stuffing.

I fully expect the Boffle solution and a closed back approach both to work very well indeed and it will be a matter of taste as to which I prefer.

All in all, I don't see (or hear) any reason why you should be cautious about buying a pair of these drivers.

As for enclosure - well I recommend the box I built.

I don't recommend Open Baffle - not because I don't think OB is good, but I don't see it as the best choice for the AN15. The reasons are - this driver is not dipole, the frequency response at the front and back are different, not least because at the front you have a whizzer cone. I also believe you can't have the driver too near the floor because then the high frequencies are too low relative to your listening position, yet placing the driver at ear height will mean inadequate bass. This forces you to add another driver. And for me, this negates the benefits and purpose of choosing the AN15 in the first place. An OB in my view is better served with a 4" to 6" full range and supported by a 15" woofer.
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Old 2nd June 2013, 03:59 PM   #322
Bigun is offline Bigun  Canada
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UPDATE


I've been using the AN15 in the box, open backed, for a few months now. The amplifier has been my Cellini SET.

I have found a few things so far - the bass goes reasonably deep but it's a bit laid-back and it sounds as if there are some holes in the mid bass response, probably a consequence of the open backed box that I'd like to fix at some point. The treble is not as clean as I would like - this speaker is big and relies on a whizzer and a phase plug. It isn't well suited to near field, you hear a lot of stuff that doesn't sound right with your head up near the driver. You need to be many feet away.

Yesterday I switched out the tube amp for my Bryston BP60 and pulled the speaker box further out from the walls. This made a nice change. It's clearly a lot more dynamic, the bass is punchy and deep, the mids are precise and the treble is cleaner. There's still some of that open baffle suck out in the mid bass somewhere.

Clearly I have been hearing a number of limitations of my old SET amplifier (my first ever tube build and not super hi-fi). There is still some directionality in the treble and I think some peakiness (as evidenced on the data sheet) that I will address later. But my faith in this driver has been strengthened by the amplifier swap. I have never heard a full range produce such a clear and dynamic output that truly goes from deep bass to the treble. I shall have to invest some more time and effort into this speaker.
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Old 2nd June 2013, 04:24 PM   #323
IG81 is offline IG81  Canada
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I don't have time to go through the whole thread to find out if you did, but have you tried closing-off the box, giving it some stuffing and perhaps aperiodic vents?

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Old 2nd June 2013, 09:18 PM   #324
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pics ?

how deep is your open backed box ?
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Old 2nd June 2013, 11:17 PM   #325
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Quote:
Originally Posted by IG81 View Post
I don't have time to go through the whole thread to find out if you did, but have you tried closing-off the box, giving it some stuffing and perhaps aperiodic vents? IG
I have not done that yet - I'm embarassed to say. I have prepared a back piece with holes drilled but I need to buy some bolts. There are T-nuts fitted at the back of the box to accommodate it. I also need some lining material, some felt would be good. It just hasn't been a priority (yet).

Quote:
Originally Posted by norman bates View Post
pics ?
You don't have to scroll back in the thread very far to find some; post 274 shows a finished picture.

Quote:
Originally Posted by norman bates View Post
how deep is your open backed box ?
The box is 2 feet deep.
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Old 3rd June 2013, 12:38 AM   #326
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I'll review post 270 to today.

Nice box.

2' deep ?

Well, based on simple math, 1129/4' (that's where the front wave will meet the back and cause a dip, I consider a driver to start canceling at its closest edge) = dip at 280hz, but a peak around 140hz (+3db to +6db, that's where the front is 1/4 wavelength out of phase, thusly adding). Have it close to the back wall helps add the bass too.

Yea, it is doesn't go way low, but the peak really adds a loudness hump (always nice), especially to speakers in boxes without baffle step, and our lower listening levels to prevent garbling the midrange.

I'd always said you (anyone = you) need 2' minimum distance from the front of the driver to the back.

Classic theory says an open baffle with wings (straight back), the wings should not be more than 1/3 or 1/4 as long as the front width (for standing wave resonances). I know my large folded baffle (wings on hinges), it was easy to play, but having them parallel and a foam box around the backside, I didn't hear any problems, even folded back to make a triangle shaped box.

Too bad, I think you should try a 10 band eq to play with the response, and I'd imagine the dispersion is limited, thusly the reflected field would see to have less highs.

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Old 3rd June 2013, 02:57 AM   #327
Bigun is offline Bigun  Canada
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I don't have EQ on hand at the present time (could change in the future) but I might try playing with some simple analogue solutions first - and try also a closed box. I don't have plans to try it vented, the box wasn't dimensioned for a vented enclosure and I expect it will go deep enough based on a closed box if I wanted to go that route.

Norman - have you ever looked at the Boffle concept ?
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Old 3rd June 2013, 11:33 AM   #328
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no, but I like 3-4" thick foam around the back of a driver on an open baffle.
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Old 3rd June 2013, 12:23 PM   #329
Bigun is offline Bigun  Canada
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what kind of foam ?
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Old 3rd June 2013, 01:49 PM   #330
IG81 is offline IG81  Canada
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How large did this enclosure end-up being, was it the 13.6c.f?

Based on the published specs, looks like 13.6c.f sealed with light stuffing would be very good (Qtc~0.75, f3~42Hz). I would not go below 6c.f (Qtc~1.0), would use somewhat heavier stuffing (~1c.f increase in apparent Vb) and would probably make this aperiodic (Ql=2~3) to bring Qtc down and still have reasonable bass output (f3~60Hz) without ruining it for high-impedance amplifiers.

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