Subwoofers~SVS vs Tapped Horn vs Fitzmaurice THT

[DrWho]

The Bag End infrasub isn't gonna come close to any of the other options mentioned so far.....it's using a low excursion driver with poor linearity and relying on a sliding shelf filter to keep it from blowing itself up (which also keeps it from making any usable output down low). I can't find the thread on it, but it was definitely an interesting discussion.

Did Tom do the Volvotreer tapped horn design?

[Quiet_Hollow]

Did Tom do the Volvotreer tapped horn design?

Yes, I sure did.

[michael hurd]

A few years ago, I did the math on Bag End's claims, and the claims are rather ambitious. Their '97 db/w' driver is installed in a 3 cu ft box, and has a -3 db point of 70 hz. Below that there is a 12 db/octave boost built into the amp.

The Bag End Infrasub 18 claims from their white paper: ( + - 3db from 8-95 hz half space ) http://www.bagend.com/bagend/downloads/isub18.pdf

The claims are rather extravagent, and the claimed 400 watt amplifier is 'limited' to 200 watts period. With the insane amount of L/T boost they are throwing at the driver, it pretty much guarantees that the amp will clip at low output levels at any low frequency.

Here's a review of that system:
http://www.hometheaterhifi.com/volume_4_4/bagend18.html

I quote this: We could get a maximum of 103.5 dB at 31.5 Hz using nearfield testing, before the amplifier clipped.

There were no distortion measurements at all with the above testing, just an in-room response.

If you start boosting at the 70 hz knee, at 17.5 hz, you would have 24 db boost. The amplifier, whilst being claimed to do 400 watts, does 200 watts of sine wave power. ( for short term periods before thermal issues ) This equates to 24 db over a 1w level. With that in mind, if you wanted flat response to even 17.5 hz outdoors (their white paper says 2Pi, and +/- 3db at 8 hz) you can use no more than 1 watt above the knee before you run into headroom issues.

Again, if you wanted to use the full 200 watts above the knee, and still wanted to maintain flat response in your sealed box down to even 17.5 hz ( 2Pi ) you would need 50 kw of amp. ( 200 watts @ 70 hz, 24 db of boost @ 17.5 hz = 50,000 watts )

[Quiet_Hollow]

Not to de-rail the thread, and I'm not standing in blind defense of the Bag End design....but from a strictly technical POV that review is just that, a review. I'd be very skeptical about any objective conclusions drawn from his data.

[artto]

WOW. OK. A lot to consume here.

Rob ~ I've been fine. Hope everything is going your way too!

So, lets see. I always suspected something a little "corny" with the Bag End stuff. An EX-friend of mine who's become increasingly delusional in recent years is big on them. I kept explaining to him that this is for a HIGH FIDELITY system, not a night club but I guess he doesn't get it. I've also played bass through one of their ELF systems years back and didn't like it very much. I thought maybe this new INFRA thing might be better but I guess not.

My wife & I went to the Chicago Museum of Science & Industry last week and attended the OmniMax theater. They seem pretty proud of their 20KW sound system, and it's subwoofers. The show was about building the Canadian Pacific RR. I have to tell you, the sound, the subwoofers sucked. That's exactly the kind of sound I don't want to end up with. That isn't the way a train or locomotive sounds. Hell, even my existing system can do better. I've played the Danley demo recordings of the coal train and train startup on it and its way better than what I heard at the museum!

It looks like a tapped horn across the right wall firing into the right rear corner or multiple drivers mounted in the rear wall at that same corner under the hallway stairs using the other side of the basement as an infinite baffle. That way I'm not messing up the visuals across the front of the room, nor am I using up any more floor space since the tapped horn (like the volvotreer) will simply replace the riser under the record cases. I don't know if it will matter much at those frequencies but the infinite bafffle setup has the drivers farthest from my neighbors side of the house and the drivers would be facing west towards the front of the room (nieghbors on south side). They haven't complained in years but I haven't been using a 800 watt Hartke 4x10 + 2x15 bass rig down there anymore either [li]

[tragusa3]

I may be mistaken, but that may be the IMAX that Danley outfitted with four of the TH50's?

[CECAA850]

Art, I'm not as familiar with your room as some. Will the sub be somewhere in the same vicinity as your mains? You want to avoid having the sub behind you if possible.

[DrWho]

Have you considered the localization of the subwoofer located behind and to the right of the listener?

[DrWho]

Art, I'm not as familiar with your room as some. Will the sub be somewhere in the same vicinity as your mains? You want to avoid having the sub behind you if possible.

Haha, overlapping posts - I was thinking the same thing.

[artto]

I may be mistaken, but that may be the IMAX that Danley outfitted with four of the TH50's?

I don't know. I have a call into them. I know they said "Four subwoofers". We'll find out shortly for sure.

[artto]

Have you considered the localization of the subwoofer located behind and to the right of the listener?

Mike and Carl, yes I have. I was "hoping" that at such low frequencies it wouldn't matter much, if at all. The distance is about the same to the listening position, slightly closer, as the L&R mains. The center speaker would be closer.

Couldn't I introduce a slight delay to the subs if I have to? Or do you really think the localization will be an issue? That is one of the reasons I kind of liked the twin SVS solution. They kind of fit in across the front without being too visually intrusive. I even thought of placing a "fake" column made of masonite in front of them to blend in with the polycylinders. And I thought they might integrate sound wise a little more seamlessly in that location. I really don't like having a bunch of equipment piled up across the front of the room, be it speakers or flashing lights and glowing tubes. I think it kind of ruins the whole illusion.

Another thought was to use a pair of tapped horns the same way. But the horn Tom built is a little too long to stand veritically in the room.

[CECAA850]

If you cross them low enough it may not be an issue but I'd hate to take that chance. I've never had good luck with subs behind me, but maybe that's just me. I'd think that if they were somewhere close to the same planes as your mains you'd get better results.

[artto]

I may be mistaken, but that may be the IMAX that Danley outfitted with four of the TH50's?

I don't know. I have a call into them. I know they said "Four subwoofers". We'll find out shortly for sure.

Yikes. I just went to the Danley website and surprise, surprise, surprise. They say the Chicago Museum of Science and Industry uses their sound system.

I have to tell you, that low end was just a bunch of rumbly noise. I'm a train buff. And that just doesn't sound like any train I've ever heard. I even took my dog to Downers Grove where I used to live to get him used to trains on the BNSF 3-track mainline - he had to go for training at a facility that was near train tracks and the sound scared the bajeeba's out him, especially since he couldn't see it from inside the building. While we were in Downers Grove a large coal train started up and came off a siding, along with a passing frieght, and then an Amtrak Zephyr. That's not the kind of sound I heard at the OmniMax. Like I said, my existing system reproduces that better than the Museum's setup, with Danley's own demo recordings no less!

[CECAA850]

There's a scene in the "Polar Express" where a train pulls up in front of the main characters house. The scene starts showing items around the room vibrating from the rumbling train. At this point, all you hear is the things jingling around the room but with the IB, you feel the vibrations of the train on the track (but you actually don't hear the train yet). The sound builds to where you eventually hear the train and the whistle and your couch is shaking pretty good from the engines vibration. By the time the train stops in front of the house, you can feel every pulse of the steam piston. It's the most realistic sound (and feel) of a train I've ever heard.

[artto]

There's a scene in the "Polar Express" where a train pulls up in front of the main characters house. The scene starts showing items around the room vibrating from the rumbling train. At this point, all you hear is the things jingling around the room but with the IB, you feel the vibrations of the train on the track (but you actually don't hear the train yet). The sound builds to where you eventually hear the train and the whistle and your couch is shaking pretty good from the engines vibration. By the time the train stops in front of the house, you can feel every pulse of the steam piston. It's the most realistic sound (and feel) of a train I've ever heard.

I agree. That's how a train (should) sounds. But that's not what it was like at the museum. I kind of get that on 2-channel system but not quite enough down really deep. You can feel the concrete floor under the carpet carrying the vibration, but there's none of that rumbly noise which is just plain irritating IMO.

EDIT: Maybe I don't need subs? The room resonance around 19Hz is doing it's job? Trying to integrate something more just detracts more than it contributes?

[DrWho]

Have you considered the localization of the subwoofer located behind and to the right of the listener?

Mike and Carl, yes I have. I was "hoping" that at such low frequencies it wouldn't matter much, if at all. The distance is about the same to the listening position, slightly closer, as the L&R mains. The center speaker would be closer.

Couldn't I introduce a slight delay to the subs if I have to? Or do you really think the localization will be an issue? That is one of the reasons I kind of liked the twin SVS solution. They kind of fit in across the front without being too visually intrusive. I even thought of placing a "fake" column made of masonite in front of them to blend in with the polycylinders. And I thought they might integrate sound wise a little more seamlessly in that location. I really don't like having a bunch of equipment piled up across the front of the room, be it speakers or flashing lights and glowing tubes. I think it kind of ruins the whole illusion.

Another thought was to use a pair of tapped horns the same way. But the horn Tom built is a little too long to stand veritically in the room.

Knowing how critical of a listener you are, I'm pretty sure you're going to notice it - even with the most intense xover and delay settings. You can just feel that the pressure is greater on the side that the subwoofer is located.

Btw, it would be pretty easy to redesign a tapped horn or even custom design one to fit into the aesthetic constraints of the front of your room.

In regards to the Omnimax, the source material or system configuration could have just as much of an impact on the sound. It's not uncommon for theaters to crank the subs since the average population think it's more exciting......

[artto]

From the Danley website:

"Chicago Museum of Science & Industry - Chicago, IL: MediaMerge of
Chelsea, Alabama replaced an aging AV system in Chicago's only
five-story, domed IMAX theater, located in one of the country's busiest
museums. They installed four Danley Sound Labs TH-50 subwoofers and six
Danley Sound Labs SH-96 loudspeakers in a one-for-one swap with the old
equipment."

Sounds like my old, beloved museum got taken on this one? "one for one swap with the old equipment? Hmmm.....sounds like the old stuff was more valuable than the new. Someone made out like a bandit!

And BTW, the picture was pretty distorted too. Most of the time it was difficult to tell if something was actually curved or straight, except for the locomotive of course. The locomotive often looked like the Polar Express locomotive climbing that sprial grade up the mountain, bending around it.

[artto]

Btw, it would be pretty easy to redesign a tapped horn or even custom design one to fit into the aesthetic constraints of the front of your room.

In regards to the Omnimax, the source material or system configuration could have just as much of an impact on the sound. It's not uncommon for theaters to crank the subs since the average population think it's more exciting......

Thanks Mike, I'm sure it is, except I don't know what the parameters are. It really only needs to be a few inches shorter than the volvotreeter.

In regards to the source material or system configuration, yes, that had crossed my mind but it was so amazingly bad. It reminded me of the old movie "Earthquake" with those Cerwin Vega subs installed in the theaters showing it. Practically made me sick.

[CECAA850]

EDIT: Maybe I don't need subs? The room resonance around 19Hz is doing it's job? Trying to integrate something more just detracts more than it contributes?

You'd be surprised how much infrasonics add to the experience.

[artto]

Mike, you mentioned something about the amplifier needed for driving this.

I was thinking of this: http://www.guitarcenter.com/Crown-XLS1000-DriveCore-Series-Power-Amp-105803787-i1516454.gc

What would you suggest? The old Crown DC300 went down to DC at full output I think. My PSA2 might too or close to it.