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High fidelity subwoofers

hvbias

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These tower subwoofers seem to be popular in the high end, one such example posted below is a sealed tower using 4 10" Scan Speak drivers. Would there be standing wave cancellation between the drivers? If not what other downsides are there besides being large and expensive? (those compromises are fine with me)

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The lower limit of my bass horn is going to be 80-100 Hz so I am looking for the highest fidelity stereo subs on either sides of the speakers with no compromises. In keeping with my philosophy of strong emphasis on the speaker quality, DSP crossovers and room.

These will be separate from either distributed bandwidth limited subs ala Geddes or Welti, I have not decided on those cancellation/room smoothing issues.
 
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SIY

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At 80 Hz, the wavelength is about 12.5 feet. So you're not really building up a wave in that cabinet.
 

DonH56

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At 80 Hz the wavelength is about 14' (1127 ft/sec / 80 Hz). Drivers need to be within about 1/2 wavelength to couple so as long as the cone centers are within about 7' you should be OK. I use 1/4 wavelength to minimize other artifacts and such but 3.5' is still a long ways... (Edit @SIY beat me to it.)

I went with Rythmik because they have a lot of output in a fairly small box and use a servo circuit that improves upon the old scheme I used in my DIY sub ages ago. Plus Brian Ding, the man behind Rythmik, is a very sharp, very nice guy with a day job similar to mine. The servo circuit reduces a variety of distortion mechanisms in the subs.

http://www.rythmikaudio.com/

That said, the HT revolution has led to development of a lot of very good subwoofers these days...
 
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hvbias

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At 80 Hz the wavelength is about 14' (1127 ft/sec / 80 Hz). Drivers need to be within about 1/2 wavelength to couple so as long as the cone centers are within about 7' you should be OK. I use 1/4 wavelength to minimize other artifacts and such but 3.5' is still a long ways...

I went with Rythmik because they have a lot of output in a fairly small box and use a servo circuit that improves upon the old scheme I used in my DIY sub ages ago. Plus Brian Ding, the man behind Rythmik, is a very sharp, very nice guy with a day job similar to mine. The servo circuit reduces a variety of distortion mechanisms in the subs.

http://www.rythmikaudio.com/

That said, the HT revolution has led to development of a lot of very good subwoofers these days...

For music use (a concert grand extends fairly low) wouldn't as little excursion as possible be desirable? This is what attracted me to these multiple driver beasts.

I realize companies like JL Audio put large sums of money into designing high excursion drivers that are also low distortion, but an off the shelf 1 or 2 driver in a box? This is not a knock on Rythmik, just thinking out loud. With Class D being so efficient, something like a 1000 watt amp on the bass towers is small, produces little heat and doesn't need to rely on a servo.

Box size is no issue for me, the main speakers from 80-100 hz up will be at least 5-6' and they are going in a large room.
 

DonH56

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Many ways to skin the cat... Small excursion generally means lower distortion but to get the same SPL larger drivers and/or enclosures with multiple drivers. If you've the space that's a great solution, and larger boxes usually means greater sensitivity as well. Servo does compensate for some forms of distortion beyond nonlinear excursion, however, and can greatly lower the effective output impedance of the amplifier seen by the driver. A big part of a sub design is the Q of the system and amplifier that controls the cones without ringing and such. Multiple drivers with lower excursion are not necessarily better in that regard. I have never really understood the bias against servo but I'm an engineer, not an audiophile, though at times have laid claim to both. To my mind adding servo to a good base design can help improve the sound further. YMMV.

There is low-frequency content in a lot of music; my foray into subwoofers began long before the HT days. Drum strikes, piano and xylophone hammer strikes, organs (natch), plucked strings on guitars, and many more add a bit of deep, deep bass that I found added to the musical experience.

IIRC the lowest fundamental on a standard (88-key, not the big 96-key Bosendorfer) concert grand is 27 Hz.

Mark Seaton has made large multidriver systems sans servo and he is highly regarded... Funk Audio has about the best measured performance around, is also highly-regarded, and does not use servo. Salk makes great cabinets but uses Rythmik kits so would be excluded. I have not heard Hsu in ages, never heard PSA and have no real research about them, I liked Paradigm and JL but to my ears Rythmik is comparable or better for a fraction the price, and my last few experiences with Velodyne have not been great. SVS is highly-regarded and is winning a lot of awards but I've never seen one so no personal experience.

Hopefully others with more expertise and experience will chime in...

HTH - Don
 
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SWL3600

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My two cents is that after owning several DR subwoofers, I went the horn loaded route and haven't looked back.

They're big but you said that ok with you. They have ultra low distortion and do not rumble, lag behind or fart out artificial boomy bass. Only clean, smooth, natural, tight punchy bass that just oozes out of your mains. They integrate so effortlessly.
 
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hvbias

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My two cents is that after owning several DR subwoofers, I went the horn loaded route and haven't looked back.

They're big but you said that ok with you. They have ultra low distortion and do not rumble, lag behind or fart out artificial boomy bass. Only clean, smooth, natural, tight punchy bass that just oozes out of your mains. They integrate so effortlessly.

This was something I was considering early on, but they seem to have one too many compromises for me, primarily the designs I have looked at require corner placement (I am pulling my main speakers further into the room) and/or require EQ to correct the response. I'm already going to be using EQ below Schroeder I'm not sure I'd want additional correction on the subwoofers. But I certainly haven't ruled it out if I find a design I like.
 

SWL3600

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I hear ya. It kinda worked out for me because even though my subs (2) are 15x18x72 inches tall, I have them in a corner standing upright and it's not so bad (I keep telling myself that).

I had to use a Mini-dsp 2x4 hd to change the slope on these because otherwise they play up to 90 hz even if I set my xover to cut them off lower. Once I figured this out, these subs are GOLD. I play them just under where my mains roll off (36hz) for music only. Mini DSP takes care of the subs and a DEQ2496 EQ's the mains to the room in addition to bass traps, diffusion and absorption at the first and secondary reflection points.

I've HAD a lot of DR subs and have HEARD a lot of DR subs and none play as clean and right as these horn loaded subs. Not only are they clean with very little distortion (if any) they have output that is incredible. These are the THTLP subs from Bill Fitzmaurice.
 
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hvbias

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I hear ya. It kinda worked out for me because even though my subs (2) are 15x18x72 inches tall, I have them in a corner standing upright and it's not so bad (I keep telling myself that).

I had to use a Mini-dsp 2x4 hd to change the slope on these because otherwise they play up to 90 hz even if I set my xover to cut them off lower. Once I figured this out, these subs are GOLD. I play them just under where my mains roll off (36hz) for music only. Mini DSP takes care of the subs and a DEQ2496 EQ's the mains to the room in addition to bass traps, diffusion and absorption at the first and secondary reflection points.

I've HAD a lot of DR subs and have HEARD a lot of DR subs and none play as clean and right as these horn loaded subs. Not only are they clean with very little distortion (if any) they have output that is incredible. These are the THTLP subs from Bill Fitzmaurice.

The issue is with how high they need to play up to the lower midbass straight horns, which are pretty large. I am absolutely convinced in my mind that straight horn bass is the way to go from 100 Hz up after hearing its startling clarity with piano/orchestral recordings. But I do not have the same experience with subwoofers below that. I would not rule myself from trying them out given my aww with the straight bass horns.
 
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