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Old 4th January 2015, 02:05 AM   #1
chops is offline chops  United States
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Talking Pensil design using quad Alpair 10.2's...

Okay, so I figured it would be best to start my own thread about this rather than clogging up another existing thread of someone else's. http://www.diyaudio.com/forums/marka...-pensil-6.html

As I stated in that thread, I have a pair of barely used Alpair 10.2's that I want to work with. I'm tired of seeing them going to waste in the closet. I was reading through that thread above about using dual drivers in a Pensil design. I want to do the same, only using larger drivers and twice as many. Yes, I want to use no less than four Alpair 10.2's per enclosure.

I want to make this a 1.5-way design, rolling off the two bottom drivers at a certain frequency to help out with bass duty, sharing the load and drastically reducing excursion and distortion while reinforcing bass output to create a more "full range" speaker. I want to avoid subwoofers altogether as that's an added expense I don't want as well as more clutter and room in an already limited area.

I've read that the CHR 70's are capable of output into the upper 30Hz range in a Pensil. Since I have 10.2's which are already capable of lower extension, I should have no problems reaching down into the low 30's or possibly upper 20Hz range with four of them running per channel.

Size of the enclosure is not an issue as I'm used to somewhat large enclosures already. I own a pair of NHT 2.9's which stand 40" tall and 22" deep. I'm currently borrowing a pair of Polk Audio RTi12's which are nearly 50" tall and 20" deep. If I had to guess, I'd say Pensil's large enough to properly load a quad of 10.2's would probably end up being around the size of the Polk's or something close which is completely fine with me.

Of course, I'm not committed to just the Pensil design. I'm open to any design that will allow these drivers to perform, meaning really good bass extension while staying crisp, tight and detailed in the bass, excellent mids and vocals which these MA drivers are known for, natural, smooth highs and an accurate, clean, balanced sound overall.

On a side note, I was speaking to one of my car enthusiast friends today, and he's an engineer at a milling shop with several big CNC machines. I just so happened to ask him if they do custom projects on the side and if they are capable of working with wood. He told me with great enthusiasm a big "yes"! He said that all I have to do is come in sometime with some sketches or plans and they'll work me up a quote. They can also do one-off parts for pretty much any project, using pretty much any kind of material you can think of! So guess where I'll be going to get some really nice enclosures cut!


So there you have it. That's the crazy idea I have running around in my noggin at the moment. Please, PLEASE join in here and give me some direction. It's been so long since I've actually attempted designing or building speakers, I've become a bit rusty on some things. And honestly, when it comes to enclosure designs for these Alpair drivers, I'm really green. I've only every really dealt with standard drivers and multiway designs or just subwoofer systems. Eventually, I want to come up with my own designs and go from there, but I want to start off right with something I can proudly use on a daily basis and keep me going in this field again.

Dave (planet10) helped me out a LOT in my last little modding project... A 2-way tower with Vifa woofer and Fostex FE103E... Actually, a bunch of helpful members did, but I think it was Dave that originally helped me with the simple series x-over for that project.

Click the image to open in full size.


I look forward to moving along with this new project and hope to get a lot of learning done along the way!

Many thanks in advance!
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Old 4th January 2015, 03:00 AM   #2
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Quote:
Originally Posted by chops View Post
... I have a pair of barely used Alpair 10.2's that I want to work with. I'm tired of seeing them going to waste in the closet. I was reading through that thread above about using dual drivers in a Pensil design. I want to do the same, only using larger drivers and twice as many. Yes, I want to use no less than four Alpair 10.2's per enclosure.
You already have 4? Or just the pair mentioned? If the latter you are now on a search for a 2nd set of A10.2.



Quote:
I've read that the CHR 70's are capable of output into the upper 30Hz range in a Pensil. Since I have 10.2's which are already capable of lower extension, I should have no problems reaching down into the low 30's or possibly upper 20Hz range with four of them running per channel.
4 won't give you more extension, just more omff...

Quote:
Size of the enclosure is not an issue as I'm used to somewhat large enclosures already... Of course, I'm not committed to just the Pensil design.
Twin Pensil would double the cross-section and the vent area. If really big is not an issue you could consider stacked Frugel-Horn XL, or the Twin Mar-Ken10.2TT (won't go as low).

Click the image to open in full size.

There is also a rectangula version:

Click the image to open in full size.

dave
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Old 4th January 2015, 03:10 AM   #3
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Go FAST. Use a real woofer on the bottom. The magic happens on the top. The Alpairs are great on the top, but give them a break on the bottom. Intermodulation/doppler/phase distortion is real. if the XO is below 250Hz or so, IM is reduced to near zero.

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Old 4th January 2015, 03:58 AM   #4
chops is offline chops  United States
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Quote:
Originally Posted by planet10 View Post
You already have 4? Or just the pair mentioned? If the latter you are now on a search for a 2nd set of A10.2.

4 won't give you more extension, just more omff...

Twin Pensil would double the cross-section and the vent area. If really big is not an issue you could consider stacked Frugel-Horn XL, or the Twin Mar-Ken10.2TT (won't go as low).

Click the image to open in full size.

There is also a rectangula version:

Click the image to open in full size.

dave
Hello Dave!

No, I'm not in search for another pair of 10.2's. I'm in search for THREE more pairs. Remember, I'm going for a total of FOUR 10.2's per cabinet/channel.

I know more won't give me more extension. What I'm looking for is more "oomph" as you said. Clean, clear, crisp output top to bottom with nothing but EIGHT 10.2's running. I was just saying that if the CHR 70's are capable of upper 30's, I should be able to get lower than that with the 10.2's.

I want to keep the enclosures somewhat simple, meaning no horn designs. Size isn't much of an issue, but I don't want them standing 7' tall either.




Quote:
Originally Posted by Bob Brines View Post
Go FAST. Use a real woofer on the bottom. The magic happens on the top. The Alpairs are great on the top, but give them a break on the bottom. Intermodulation/doppler/phase distortion is real. if the XO is below 250Hz or so, IM is reduced to near zero.

Bob
Hi Bob!

I live in an apartment and don't play my system loud. Maybe 80-85 dB max if I had to guess. The 10.2's have a healthy Xmax of about 8.5 mm one way, so having four of them per enclosure sharing the load, they should simply be coasting along. Efficiency isn't a problem as I have plenty of power to feed them with, at pretty much any impedance. My Odyssey Audio Khartago Kismet amp is safely capable of a 1 ohm load, and it pumps out 160 watts @ 8 ohms. Again, apartment living isn't going to get me anywhere near any of those numbers in real life.


Also, as a side note, just to get me back into the swing of things, I drug out my old 2-way project towers with the Vifa woofers and Fostex 103's and connected them to my main rig. After a couple hours of playing, they're loosening back up. I forgot how good these little buggers sounded.
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Old 4th January 2015, 05:03 AM   #5
zman01 is offline zman01  Bangladesh
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Chops,

Not to distract you from your goal, but since you are planning for a considerable amount of cash outlay in 6x Alp 10.2 drivers (if at all available...), possibly you can look at these for (another) clean, powerful sounding system:

Post # 51 at ALPAIR 7P & ALPAIR 12PW combination.

Post # 174 at ALPAIR 7P & ALPAIR 12PW combination.

Not sure if the above-mentioned are too different from your existing combo (hence mentally stimulating enough...).

All the best!
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Old 4th January 2015, 06:24 AM   #6
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Quote:
Originally Posted by chops View Post
No, I'm not in search for another pair of 10.2's. I'm in search for THREE more pairs.
Fnd the drivers, then we can talk.

I can see using a pair, going to 4 makes less sense than adding a big helper woofer.

dave
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Old 4th January 2015, 07:09 AM   #7
chops is offline chops  United States
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Perhaps Bob is right. Maybe I should look into a "FAST" type system. Or rather, a fullrange driver with woofer "technology". LOL

The more I sit here listening to my old 2-way system with Vifa woofer and Fostex FE103en, the more I really like what I'm hearing. Of course, this system was just thrown together using a simple series network and never really fine tuned. Well, it kind of was, but still only used a hodge podge of parts more than anything else. The end results however is a totally different story.

Vifa no longer makes this P21WO-20 8" woofer, however Scan-Speak does. It's virtually the same exact driver with I think the same exact T/S specs, model #P21WO20-08.

Back to my 2-way system, this Vifa driver in the 2.34 cf vented enclosure is tuned to 28Hz, and let me tell you, this thing thumps and reaches deep. Even at low volumes, it's getting down there in the lowest octave quiet easily. The bass is tight, textured and musical. It's not heavy, it's not lean, it's not one-note.

That little basic Fostex driver never ceases to amaze me. At first listen tonight, this system sounded like crap. Bass sounded weak, mids and treble sounded thin and disconnected, the upper mids sounded out of phase, treble was lacking. It was a very disappointing, confused sounding bit of kit. Then after a couple hours of running (these speakers sat over 3 years without use), everything just kind of gelled together the way it should, and these little Fostex drivers are really shining. A perfect blend with the woofer, excellent vocals and overall midrange, crisp, extended treble (no need for a tweeter), a wide and deep sound stage, and imaging seems to be spot on. Other than the old Magnepan's I used to own and some small bookshelf speakers, these speakers produce a believable sound stage and image. The NHT's and Polk's don't even come close. Quite honestly, everything that has to do with the little Fostex blows the NHT's and Polk's clear out of the water.

BTW, listening to some Pat Metheny right now... Wow! Immediacy, tonality, smoothness, impact, space, dimension... It's all there in spades, and all of this at whisper levels!



So here's my current thinking... Why not go with two pairs of the new Scan-Speak 8" drivers and do two of them per enclosure, then instead of using the 10.2's, get two pairs of the more favorable Alpair 7A Gen3, again, using two per enclosure?

This would still be a simple design enclosure wise. Double the woofers will get me the extra headroom and oomph when watching movies or listening to pipe organ music. Even though I don't play my system loud, it still helps with that kind of material as there can be some major bass swings, even at lower volume levels.

Likewise with going with the Alpair 7A Gen3 drivers. They're smaller so can be mounted closer together without worry of comb filtering coming into play, plus they seem to be voted about the best out there in the MA lineup for overall vocal and midrange reproduction, not to mention they extend up beyond 30kHz. Definitely no need for tweeters with these guys. Using two per channel will also allow them to better keep up with the dual woofers.

Of course, and this is always the tricky part for me it seems, is the crossover. Would it be better sticking with a simple series network like what I'm using now, or should I step up to a finely tuned parallel network? I'm thinking the latter for such a system. However, I could be wrong. Wouldn't be the first time and certainly won't be the last time.


I know, it's typical of me to completely change the game plan as I already have here. It does seem to be a bit of a waste using two pairs of 10.2's just for bass reproduction which was another reason for thinking of going a different route.

Since I already know from experience that a setup with an actual woofer and a fullranger is quite successful, then I should be able to go into this new project rather confident of the outcome. Of course, I will still need guidance along the way, especially since I've been out of the loop for so long.

Thoughts, suggestions, complaints?
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Old 4th January 2015, 10:35 PM   #8
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I'd strongly concur with Bob's post above - FAST / 2way, whatever you want to call it.

There are numerous ways to accomplish that - but for the total budget contemplated with the multiples of 10.2 per side, I think you'd be much further ahead with a single FR driver and "real" woofers ( i.e. Not a home theatre atmospherics effect pounder) , crossed over in the 200-300Hz range

As is just so happens, that's what I've been playing with this afternoon - alternating between A7P / MAOP7 and dual A12PW, powered by Onkyo TX NR818 - a rather user friendly piece once you get used to it ( and of course requires a monitor screen to navigate the layers deep menus) and certainly very flexible for exactly this type of mucking about

For a strictly audio computer based system something like the nanoDSP and say TPA3116 for the wide banders, and Crown XL1000 for the woofers could be pretty stunning (gee, that sounds like a familiar set up)
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Old 4th January 2015, 11:45 PM   #9
chops is offline chops  United States
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Originally Posted by chrisb View Post
I'd strongly concur with Bob's post above - FAST / 2way, whatever you want to call it.

There are numerous ways to accomplish that - but for the total budget contemplated with the multiples of 10.2 per side, I think you'd be much further ahead with a single FR driver and "real" woofers ( i.e. Not a home theatre atmospherics effect pounder) , crossed over in the 200-300Hz range

As is just so happens, that's what I've been playing with this afternoon - alternating between A7P / MAOP7 and dual A12PW, powered by Onkyo TX NR818 - a rather user friendly piece once you get used to it ( and of course requires a monitor screen to navigate the layers deep menus) and certainly very flexible for exactly this type of mucking about
I too concur, hence my last post.

Like I said, the more I thought about it, the more I thought it a waste to use a couple pairs of 10.2's strictly for bass duty. Just doesn't make sense really.

As for the project, I want to keep everything passive and only utilizing one amplifier and two speaker enclosures. I don't want to do DSP, active x-overs and multiple amps. I also don't want to use subwoofers of any kind.

The Alpair 12P is a very interesting driver and I know it would sound great. The only thing is its limited Xmax and power handling. Again, I don't/can't play my system loud, but I do love good bass extension with some decent grunt behind it. I don't think these guys would be able to deliver that with the pipe organ music I sometimes listen to, or even modern music like M83 or Lorde, both of which have ample amounts of bass content as well.

The people who say "music doesn't have any real bass below 40-50Hz" has been and always will be full of nonsense. Heck, I'm listening to Norah Jones' Feels Like Home album right now, track 5 - In the Morning. Listen to that track and tell me there's no "real" bass below 40-50Hz. That bass drum is pretty darn stout. I bet it's hitting down below 30Hz easy.


Anyway, yes, the A12P's are great drivers, but for that true full range extension, that's why I was thinking of going with the Scan-Speak 8" woofers that replaced the Vifa's that I have. With an Fe of 28Hz vs 44Hz from the A12P tells part of the story. Xmax isn't much of an improvement, but the $60 difference between the two is a factor to also consider.

Going with a single fullrange driver or dual, I don't know. Maybe there's no useful point of it if they're only playing from 200-300Hz on up other than simply more efficiency.
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Old 5th January 2015, 02:46 AM   #10
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Going with a single fullrange driver or dual, I don't know. Maybe there's no useful point of it if they're only playing from 200-300Hz on up other than simply more efficiency.
Unless loud is a goal, 2 FRs as mid-tweeter is a step backward from a single.

With a single A10.2 & a passive XO you will want woofwe(s) that are 90-93 dB sensitive.

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