[FredT300B]

Every few years I decide I miss having a pair of single driver speakers in my small listening room and I check to see what the latest designs look like. I've always liked Jim Griffin's designs, so when I saw his MLTL design using Mark Audio drivers the decision was made.

I just connected them up, and they're playing some quiet baroque chamber music very nicely. At first they seemed to lack midbass, but either my ears are breaking in to the new sound or they're beginning to fill out. These 47" tall towers use Mark Audio Alpair 10 six inch full range drivers. There's no bsc circuit, so the only thing between the drivers and the speaker terminals are three feet of Belden 12ga high purity copper wire.

Here's a view of the front of one cabinet and the back of the other.

[FredT300B]

Herre's the link to the enclosure plans. Mine are of 3/4" baltic birch plywood.
http://homepage.mac.com/tlinespeakers/FAL/downloads/Griffin-A10-MLTL-030611.pdf

[wushuliu]

Very nice. They will improve dramatically over the next 200 hours...

[planet10]

I just connected them up, and they're playing some quiet baroque chamber music very nicely. At first they seemed to lack midbass, but either my ears are breaking in to the new sound or they're beginning to fill out. These 47" tall towers use Mark Audio Alpair 10 six inch full range drivers. There's no bsc circuit, so the only thing between the drivers and the speaker terminals are three feet of Belden 12ga high purity copper wire.

The drivers will get better over the 1st 200-500 hrs.

Alpair10 is a nominal 5 1/4" driver.

I'd suggest doing experiments with other wire... we use 24g solid copper wire (as does Bob Brines).

What kind of amp are you using? 300B?

dave

[FredT300B]

What kind of amp are you using? 300B?

dave

I haven't tried them with tubes or with any material having very much bass. For now I'm using my favorite speaker breakin amp, a Best Buy Insignia brand two channel receiver, with a Toshiba DVD player set on repeat mode. But even at low volume levels with this equipment I can easily hear a positive difference between these drivers and the Fostex FE-166's I used in a previous project. The Fostex drivers were shouty, with little high frequency resoultion. These have a far more refined sound.

 

[FredT300B]

Here's my advice to anybody else who builds this design: wire them in phase. The bass sounds much better that way. 

After playing some classical chamber music for most of the day at a low volume with the player on repeat, I finally sat down for a serious listen to a jazz disk I'm familiar with. The problem was immediately apparent, and a quick check revealed I had reversed the connectors on one of the drivers. The bass has suddenly come alive and the image is now where it's supposed to be. These are some seriously good sounding speakers.

White wire to red terminal, black wire to blue terminal. It's not rocket science. 

[JLM]

I'd like to see some sort of reflector directly behind the driver to keep back waves bouncing directly back at the driver for two reasons.  1st, the reflections will muddy the movement of the cone.  2nd, some of the reflections will pass through the cone material and muddy the sound even more directly.  After all, why stiffen the cabinet panels when the cone is paper thin?  Don't we want to hear the original signal from the cone and no more/less?

And I recommend considering running your speaker cables directly from amp to any single driver design (why use two kinds of wire plus an extra connection?).

[FredT300B]

I'd like to see some sort of reflector directly behind the driver to keep back waves bouncing directly back at the driver for two reasons.  1st, the reflections will muddy the movement of the cone.  2nd, some of the reflections will pass through the cone material and muddy the sound even more directly.  After all, why stiffen the cabinet panels when the cone is paper thin?  Don't we want to hear the original signal from the cone and no more/less?

I agree. The back wall directly behind the driver is lined with Armstrong #420 fiberglass. I've found this stiff fiberglass used in suspended ceilings is an excellent absorber of high frequency reflections; much more so for it's thickness than the R-13 I use in larger speakers where there's enough space behind the drivers, and more so than eggcrate foam, which isn't very effective. The enclosure is also loosely stuffed with dacron pillow fill from the top to just below the driver. So there is as about much sound absorbing material as I could get into this very shallow (5-1/4" internal depth) enclosure without overdamping the transmission line.

[FredT300B]

And I recommend considering running your speaker cables directly from amp to any single driver design (why use two kinds of wire plus an extra connection?).

Dave had also recommended experimenting with other wire, possibly a much smaller gauge solid copper. I'll do this at some point. Regarding the single wire run from amp to driver, it makes great sense of you're not going to be disconnecting and moving speakers very often, but I prefer the convenience of a speaker that's easily disconnected and moved. I usually have five or six speakers on hand and a couple under construction in the workshop at any one time, and I move them in and out of the system frequently.

http://fredt300b.smugmug.com/Hobbies/Speakers/132721_kcDVmw#!i=27073926&k=S4zvX

[FredT300B]

I'll be using these speakers with an Oppo BDP-95 source and an OddWatt Audio tube amplifier in my room at the May 4, 5, & 6 Lone Star Audio Fest in Dallas. I'll be exhibiting as a hobbyist and won't be selling anything, but if somebody likes what they hear in my room they can order a kit version of the amp from Bruce Heran of Oddwatt Audio, and they can order a flat pack MLTL enclosure much like mine from Bob Brines of Brines Acoustics. Both will be exhibiting at the show along with a plethora of other full range single driver speaker manufacturers.
http://lonestaraudiofest.com/
http://oddwattaudio.com/
http://brinesacoustics.com/Pages/M10-A10/Main.html

[Brad]

Nice project Fred.
Can't wait to hear them in May at LSAF

[chrisby]

Fred - those Oddwatts look very interesting indeed - which model?

 
While they don't (yet?) have any luscious DHT offerings,  a Class A P/P EL84 with CSS loaded SRPP front end for less than $600 (I assume sans tubes) is a helluva bargain  - for a lot of situations, 5W of this kinda power is quite sufficient for a Single driver speaker

[FredT300B]

Fred - those Oddwatts look very interesting indeed - which model?
While they don't (yet?) have any luscious DHT offerings,  a Class A P/P EL84 with CSS loaded SRPP front end for less than $600 (I assume sans tubes) is a helluva bargain  - for a lot of situations, 5W of this kinda power is quite sufficient for a Single driver speaker

I'll be using whichever model Bruce provides when I see him in Dallas. Fortunately the Alpair 10.2 driver requires no baffle step compensation, which I've found necessary with most other full range drivers, and which robs them of about 3dB of sensitivity. So if Bruce provides a PoddWatt, the speakers will play nicely on that amplifier's five watts.

In the meantime, I've tried several amps with the 10.2's ranging from a 200w/ch Krell and a $100 Best Buy Insignia receiver to various single ended and push pull tube amps including 2A3's, 300B's, and a triode-wired Ella EL34 stereo amp. The speakers are not overly sensitive to amplifier topology and sound good with any of these choices.

OT: The critical test of the new speakers will come on March 30th. We're hosting blues singer Doug MacLeod in a house concert, and we're expecting about 55 guests, including about a dozen member of the Houston Audio Society. I'll have the speakers set up in the upstairs listening room and playing Doug's new Reference Recordings CD as people arrive, and a dozen pairs of critical ears will hear them for the first time.