Here's My Usher/Altec Horn Loaded Open Baffles...

[chops]

I was originally going to build an Usher Audio D2 clone, and build these OB's just as a temp thing to get the Usher 15HM drivers run in and out of my cramped bedroom. However, now that I've been listening to them since last night, I think I'm going to can the D2 clone idea and keeps these open baffles. They sound that good!

I ran the idea across several people on various forums and they swore that running horns with open baffles would never work out. Some even said that the Altec 511B horns would not work in an MTM design. Well I have news for them.

Last night once I got them up and running playing fullrange and spent about 10 minutes doing some quick tweaking, a few things were quite apparent with these beasts (more of which I noticed today)...

1) For one, the imaging, soundstaging and depth are something in the order of very, very good, properly placed bookshelf speakers. The imaging in darn near pin-point, the soundstage is well beyond the walls of the room and the depth gets right up into your face and as far back as several meters behind the speakers and back wall. VERY 3-dimentional.

2) The uniformity of sound emitted from these speakers while standing, sitting, squatting and walking around the room is amazing. The tonallity doesn't change! As long as I'm as far back as the listening position (about 9' away) or further and I move all around, walking from the left wall to the right wall, sitting or standing, the sound remains the same. These speakers have a huge sweet spot! This also includes about 95% of imaging, soundstaging and depth and any of those locations.

3) Super sensitivity OB's! Theoretically, these OB's should be 98dB efficient at 1W/1M (wired parallel into 4 ohms each channel) or maybe slightly less due to being in OB's. I thought for sure the gains would remain the same between these and the Klipsch Cornwalls they replaced (also 98dB @ 1W/1M). I can honestly say that they are NOT. These things have to be somewhere around 101+dB. They are considerably more sensitive than the Cornwalls.

4) Power and dynamics are in abundance! From the quietest passages to the loudest, these things put it out without issue. There's just a huge wall of sound that slams into the room. Playing Telarc's "Trumpet Spectacular" with the large orchestra seems very real. The most real I have ever witnessed in my room. I felt like I was back in orchestra myself when I used to play 1st chair bass. BTW, the most power I saw going into these monsters was just under 4 watts with full pipe organ, orchestra and drum roll on the last chord of the last track. I would have to say it was right around the actual volume level as actually being there durring the live performance.

5) A full, wide-range sound. These Usher 15HM drivers are not meant for OB use as their Qts is 0.30. Without any EQ at all, they roll off pretty sharp after 50Hz or so, but with a little EQ added into the mix, I'm getting strong, usable output down into the mid-30Hz range easily. Bass is very clean, very tight and very "real" with these drivers in OB's. I'm loving this!

6) Lastly, if anyone on here remembers anything about my dipole subwoofer thread from several years ago (link in my sig), I kept remarking on how difficult it was to see any kind of cone movement from the drivers with moderate to loud volumes with low frequencies. The same is true with these new OB's! Like I said, they're playing fullrange right now, so they're getting the entire range of sound and handling it all with great ease. The reason I think they move so little is because I'm only pumping a max of about 4 watts into them, which is obvioulsy nothing to them. The simple explination is that they are hardly doing any work to produce lots of loud, clean sound into the room.

Anyway, enough gabbing. I know you all want to see some pictures, so here they are! Enjoy and please feel free to ask questions.

[mashaffer]

Yes, the first thing I noticed about OB is that the sound quality was very stable throughout the room (and to some extent the whole downstairs) even when running 8" fullrangers. It must have something to do with power response or something else that is over my head.

The only thing that surprised me about your post is that speakers with such pitiful Qts have provided such strong bass. Maybe it is due to their large diameter.

mike

[pedroskova]

Where are you crossing the Ushers over? I'm not familiar with them ...maybe I should wander over to PE and have a look.

[Pano]

Hi Chops! Good to see your Ushers came and that you have put them to good use. They look like excellent drivers, always thought about getting a pair on sale.

I am puzzled by your quoted effeceicies, tho. If you are running the drivers in parallel, then you would gain 6dB over a single driver at the same voltage but that would mean twice the power, of course. Certainly worth doing.

Also very surprised that you are really getting that much out of them in low end. Yeah, you've got a really big baffle going there- and some corner loading - but open baffle just rolls off so much in low end.

With low Qts driver like that, I would think they would need a lot of EQ to keep the low end up. That means more power at the bottom end to keep the 15s in a flat FR.

I have been running a similar rig, see the photo below.
Much like yours without the top half. 811 horn instead of your 511. Selenium 15WP3 instead of the Ushers. The Selenium has a higher Q, about 0.6, so a little more bump on the bottom end than the Ushers.

My rig has NO bottom end without massive FR tapering. Gobs of beautiful mid bass, sounds fantastic on orchestral works, but real low end energy just isn't there without bass boost under the baffle roll of frequency.

Of course your big baffle and corner loading will help a lot, I'm just curious how much. Mine, with side wings, started to roll off fast under about 150Hz. Since your baffle is taller, but about the same width, I'd guess yours rolls of under ~100Hz.

Don't mean to be a party pooper, 'cause I really like the concept - but once the novelty of the clean OB bass wears off, you'll find you don't have much real low end, unless you EQ the hell out of it.
That has certainly been my experience.

Anyhow, great looking rig. I know how good it can sound, I've got one that's 3/4 of yours. Just don't be afraid to roll off those 15s and throw some power at them to keep the bass up. OB really needs it!

BTW, what's your x-over to the 511?

[chops]

Hey there Panomaniac! I won't argue, they are nice drivers for sure.

I keep forgetting that it would be a 6dB gain. I'm always thinking it's only 3dB for some reason. Then it would make sense that I felt like these were more in line with 101dB, considerably more than the 98dB Cornwalls.

The low end is pretty decent. I don't know how or why it does it, but I've stated before that this room of mine loads up pretty good in the 20-40Hz range, which is why I had such good luck with my dipole subs years ago.

As for EQ, between 30-60Hz, I'm boosted about +10dB which is getting me into those low to mid 30's. I'm powering them with my trusty Technics SU-8099 amp. It's rated for 115W @ 8 ohms and I think 170W @ 4 ohms. Still, I've only seen a max of just under 10W so far, and that was pretty darn loud at the time, and that was full organ on a theater organ CD. These OB Ushers were chugging right along without a sweat and barely moving. I don't think I'll be running out of power anytime soon. LOL

I think I've seen bits of your system before. Very nice! You're baffle loos to be nearly the same size as half of mine (24" x 36"). With the high Qts Selenium, I would think you would be getting a little deeper than I am. Then again, I am running twice as many drivers, twice the baffle, and in my room. And yes, the midrange of OB's are excellent!

Don't worry, you're not being a party pooper at all. From the performance I'm getting so far with these OB's, it's certainly not a novelty. I can very easily turn off the sub and listen to music with just the OB's all the time if I want. They really do have great bass extension considering the amount of EQ'ing involved.

My crossover point to the 511 is 700Hz. I tried 800Hz, but the midrange was getting a bit honky sounding, so I had to back it down. However, that was also before I had the gains and woofer delay set better, so I might try 800Hz again and see what I come up with next time.

[chops]

Not a very interesting topic I suppose.

[Zen Mod]

Originally posted by chops
Not a very interesting topic I suppose.

nope ;
we just envy you





keep up with good work

[AJ]

"Not a very interesting topic I suppose."

Says who?

I love seeing projects like this. Between you and Magnetar, I'm finding all kinds of new ways to experiment. The 15" MTM has really piqued my interest. I just recently have had a chance to listen to my first compression driver - a B&C 250 DE250 sitting precariously on top of a midrange trap. No horn or waveguide yet, but I was amazed at the smoothness and pumped about the dynamics even when it's sitting in free air like this.



Crossing it to the 18" Dayton at 1200hz was just plain inspiring, in spite of the 3 feet distance between them. It was very easy to hear the potential of the comp driver. Thinking of them sitting between two 15's gets me pretty excited.

I really like the 2X4 construction of your baffles too. And the fact that you're making dipoles work in a room that's apparently about the size of mine, makes me want to revisit them.

Keep the posts coming Chops. A few of us like seeing them.

[Cal Weldon]

Hey chops, where's the rest of the box around the woofers?

[c2cthomas]

Hi Chops,

Yum-Yum! Looks GREAT! Please inform as to the dimensions of the baffle. Looks like about 20" x 84" (give or take a couple).

Also - is that a center channel I spy in the photo? What's the scoop on it?