Alpair 10 vs Alpair 7 - Open baffle with boxed woofer. Passive Xover. - Page 4 - diyAudio
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Old 25th November 2012, 08:32 PM   #31
zman01 is offline zman01  Bangladesh
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TimBoz,

Have you started the break-in process for the A12P? If not the it'll be good to get the hours on before cranking them up.

Last edited by zman01; 25th November 2012 at 08:41 PM.
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Old 25th November 2012, 08:45 PM   #32
TiMBoZ is offline TiMBoZ  Australia
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No break in. Drivers went straight from the box they came in onto the baffle. I have them filtered with 100uf caps at moment. Will just play them at modest volume a couple of hours each day for week or so. I need to get some sound foam to damp down some box resonances etc. Before getting more serious about tuning the XO etc.
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Old 26th November 2012, 04:04 AM   #33
chrisb is offline chrisb  Canada
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Originally Posted by TiMBoZ View Post
No break in. Drivers went straight from the box they came in onto the baffle. I have them filtered with 100uf caps at moment. Will just play them at modest volume a couple of hours each day for week or so. I need to get some sound foam to damp down some box resonances etc. Before getting more serious about tuning the XO etc.

maybe second think using foam?
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Old 26th November 2012, 03:35 PM   #34
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Thanks! That's a great idea Monte re; plywood prototype for baffle, U sides etc. I have plenty of spare 12mm plywood.

The idea of using the Alpair 10 means 'theoretically' I can use 6db (re: simple) XO's. It's a very versatile driver. The Alpair-10 is great. The Alpair-7 may be even better between 400 - 20k. But there are probably trade offs either way between the two. But, their power handling is limited. This is to be expected from very low mass drivers.

By XO at 400Hz, theoretically increase power handling. By relieving the driver of having to pat it's head (make mids/highs) and rub it's tummy (make lows) at the same. With 'full range' theoretically I can go from 400 - 20,000 that's still pretty good.

An 8gram 25mm voice coil/cone can't articulate bass like a 75mm voice coil can. Conversely, a 16gram/cone 75mm voice coil can't articulate mids/upper mids and low treble like a 25mm voice coil can. The 'pro' of full range is no XO's but the con is compromises with the driver's ability to articulate the waveform 20 - 20Khz. They are basically a glorified midrange. Hence the idea, use 6db XO to a helper woofer on the bottom and helper tweeter at top. Now, a lower XO of 150-200Hz is better on paper. Agreed. But then you start talking much bigger inductor values. Rather than a 2 mH for 400Hz, we're now talking about >4.7mH for 200Hz. Not extreme, but just this difference really does start to increase to 'focus/emphasise' the output/balance of sound coming from the woofer. At 400Hz (smaller inductor), the mix/balance between the (Morel) woofer and Alpair-10 is much better. More balanced/natural. XO at 200Hz, the mix/balance is like your listening to the rest of the band, from perspective of the bass player. The power handling is less. You don't want to be adding resistors everywhere trying to correct these imbalances. So XO at 400Hz has practical benefits.

I have practical considerations: I'm trying to keep the baffle width/size as agreeable as possible. My wife won't let me put a really great sounding, but door sized speaker in middle of the lounge room. I need to create something 'presentable', child friendly. I can't have something that looks like a science experiment with inductors, caps, alligator clips etc. lying around permanently. Hubby's generally cool with it, wifey's generally not.
tahts really interesting.
how about a xo at 300 hz. I plan on using a 12 inch eminence kappa pro from 35hz to 300hz, then let the alpair 12p do its job.
please let me know what is your results and where you thought the xo sounded the best
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Old 26th November 2012, 11:06 PM   #35
TiMBoZ is offline TiMBoZ  Australia
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Update: for what that's worth, I simulated the 12Ps, the 10's and the 7 's in 'Excel Baffle'. For what that's worth, the 12Ps simulated a generous 50Hz lower freq extension in context of my baffle width etc than 10 & 7's. Also once I received the 12P's and saw the physical size of the things, the extra Sd on offer over the 10s, I lost interest in a 12 vs 10 comparo & futzing around with the 10's vs 12P's on the same baffle. Apologies if you were interested in reading about this specifically.

After listening to the 12P and the 10's. My initial, superficial impression is that the 10 is RELATIVELY more spritely, deft, faster, lighter. More spry, modern. The 12 is heavier, very smooth, natural sounding. More graceful. Has more of a warm, vintage vibe to it. Both sound great in their own way. These are just my initial, 'superficial' impressions. In context of a PASSIVE XO, IMO the 12P will be a simpler execution, a safer bet in context of PASSIVE open baffle. I don't have any measuring equipment etc. You could use either the 10 or 12 or the 7. But in context OB (not boxed) the 10 or the 7, your XO will most likely be higher and as such the execution of XO more critical. I've opted for the simpler option IMO, on paper and going with the 12P's. Apologies if you were interested in reading about the 10s specifically.

At present I have 2 cabinets on the go: a slap together 'prototype' version 1 from 18mm MDF, a 1200 tall x 250mm wide baffle, simple box construction for the sealed woofer, deep U-frame sides etc. this is up & running. But suffers some serious resonance issues.

And a second version 2, currently the wood is cut, but unbuilt/assembled, with a 1200 x 280mm wide baffle, that has a 32mm thick MDF baffle other sections in 32mm MDF as well as 18mm MDF sections. More elaborate construction, with kerfing on some corners etc. that I'm yet to attempt. The 280mm baffle is as wide as I can go (fit in my lounge room) with WAF.

At moment I just have a rough XO with 6.9mH inductors on woofs and 100uf caps on 12Ps. The woofer are nominal 89db (approx 6.4 Ohms at XO) and the Alpair is 92db (approx 9.5 Ohms at XO). At XO approx 60% of amp power goes the woofer, 40% goes to the Alpair. I can say the sensitivity balance between the woofer/FR drivers is fine TO MY EARS. In my room, there is plenty of bass, forgeddabowdit. Almost too much bass. Also with the full range there is no sense of 'boom/tizz': when a relatively sensitive tweeter can sometimes sound/present as a bit 'forward of, or on top of' a woofer at low volume levels.

After playing around with some foam on the prototype version 1, in the U-frame etc. the foam doesn't really fix the 'colorations' caused by the large sections of undamped MDF. When you have a conventional tweeter you have this nice little metal flange, assembly etc. that is in itself very well damped. When you put a big full range driver on a large undamped MDF box/u shaped baffle, it rings like a bell. But I'm not going to put too much time/effort into damping/developing the prototype version 1. It can't be done effectively with 50mm sound foam alone. The purpose of the quicky version 1 is to verify that there isn't some fundament flaw in the concept/driver choice. It also helps to take the some of the 'excitement induced rushing' out of the build of version 2, so you can just concentrate, take your time on the woodwork when you're building the 'keeper'.

From here, I'm going to use my electric guitar tuned to concert pitch, into a compressor, into an guitar amp, into the A12. By heavily compressing the signal from guitar, using the front pick up, a clean amp setting, (it will sound almost like a keyboard) and playing pitches between 82Hz > 440Hz to get a feel for the roll off of the A12 in situ/on the baffle. I'll try some large cap values > 80uf to settle on best compromise between lowest possible XO point/filtering from low bass signal/acoustic roll off of OB. Hopefully it'll be around 150 – 200Hz. Once I've settled on these cap values - I'll just use inductors to 'fit' the sealed woofers underneath based on Zmin 6.4 Ohms for the woofers, So far all indications suggest it's going to work out great once a properly damped enclosure/baffle is sorted on version 2. Ill try to upload a few photos of version 1 soon…
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Old 26th November 2012, 11:25 PM   #36
chrisb is offline chrisb  Canada
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Originally Posted by TiMBoZ View Post
From here, I'm going to use my electric guitar tuned to concert pitch, into a compressor, into an guitar amp, into the A12. By heavily compressing the signal from guitar, using the front pick up, a clean amp setting, (it will sound almost like a keyboard) and playing pitches between 82Hz > 440Hz to get a feel for the roll off of the A12 in situ/on the baffle. I'll try some large cap values > 80uf to settle on best compromise between lowest possible XO point/filtering from low bass signal/acoustic roll off of OB. Hopefully it'll be around 150 – 200Hz. Once I've settled on these cap values - I'll just use inductors to 'fit' the sealed woofers underneath based on Zmin 6.4 Ohms for the woofers, So far all indications suggest it's going to work out great once a properly damped enclosure/baffle is sorted on version 2. Ill try to upload a few photos of version 1 soon…

careful with that axe Eugene
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Old 26th November 2012, 11:58 PM   #37
TiMBoZ is offline TiMBoZ  Australia
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that's a thought. Note to self: MUST NOT; NO rocking out on guitar thru 12Ps maaan
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Old 27th November 2012, 09:33 AM   #38
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my gibson rocking quite well on supravox
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Old 28th November 2012, 09:21 AM   #39
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@TiMBoZ is the 100µf elettrolitic cap ? have you tested without ?

you can use a asc motor cap as alternative way lot better ....trim a bit with bypass
I have claritycap 100µf pp on my amp way better then silmic
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Old 22nd May 2013, 12:27 AM   #40
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Originally Posted by TiMBoZ View Post

By XO at 400Hz, theoretically increase power handling. By relieving the driver of having to pat it's head (make mids/highs) and rub it's tummy (make lows) at the same. With 'full range' theoretically I can go from 400 - 20,000 that's still pretty good.

An 8gram 25mm voice coil/cone can't articulate bass like a 75mm voice coil can. Conversely, a 16gram/cone 75mm voice coil can't articulate mids/upper mids and low treble like a 25mm voice coil can. The 'pro' of full range is no XO's but the con is compromises with the driver's ability to articulate the waveform 20 - 20Khz. They are basically a glorified midrange. Hence the idea, use 6db XO to a helper woofer on the bottom and helper tweeter at top. Now, a lower XO of 150-200Hz is better on paper. Agreed. But then you start talking much bigger inductor values. Rather than a 2 mH for 400Hz, we're now talking about >4.7mH for 200Hz. Not extreme, but just this difference really does start to increase to 'focus/emphasise' the output/balance of sound coming from the woofer. At 400Hz (smaller inductor), the mix/balance between the (Morel) woofer and Alpair-10 is much better. More balanced/natural. XO at 200Hz, the mix/balance is like your listening to the rest of the band, from perspective of the bass player. The power handling is less. You don't want to be adding resistors everywhere trying to correct these imbalances. So XO at 400Hz has practical benefits.

I have practical considerations: I'm trying to keep the baffle width/size as agreeable as possible. .
great to read this, pretty much spot on. I'd like to make a simple all aluminium cone design w/ 1st order OB paired to helper woofer -
I wd cross at 425-450hz as a first order (a 6db roll off isnt going to be too much of a waste of midrange). The cap values are not silly at that x/o point(I always use Clarity caps). I'd like to use a dayton RSS210 subwoofer per side, as they can be crossed as high as a standard 8" woofer and are relatively low mass. They do bottom out easily at their Fs but since this is not a high power build and using 1 per side, shd be ok.

Last edited by Bill poster; 22nd May 2013 at 12:32 AM.
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