11,000 ft^3 room: need a bass solution (50-500hz) to keep up with large format horns

steve71

Member
2007-11-12 6:01 pm
Back story:

I'm in the early stages of building a new home theater / listening room in an out building on my property. The building is already in place (28x38x10.5ft).

I want to build a set of 6/7 speakers. They will be three way actives. Above 300-500hz I have covered with Altec horns (multi cells and matrarays) with 288 drivers & Gauss HF horns above 5Khz. Below 50hz will be covered by four of Ricci's GJALLARHORN tapped horns.

I built a couple of front loaded bass horns for stereo listening with GPA 515G drivers and they are great, but I don't want to build another 4 or 5 of them. Besides, they only play to 80hz and I'd rather cross to the subs at 50-60hz.


So I'm thinking either a sealed or ported cab with a pair of pro 15" or 18" drivers. Budget is under $300 per driver since I have to buy 12 or 14 of them :eek:. Maybe I should consider singles for the surrounds?

The Onken W cabs look interesting, but they also look like a bit of a headache to design.

At fist glance, the B&C 15TBW100 (B&C SPEAKERS) looks good in a simple bass reflex cab. Two of them together should give me around 97db/w/m with 3000 watts rms.

Their 18", 18 TBW100 (B&C SPEAKERS) offering looks good too. Higher sensitivity and a stated bandwidth of 35-1Khz.

(Q 1) Will using these 18's compromise sound quality in the 200-500hz range as compared to the 15" drivers?

(Q 2) With the active x-overs it will be easy to time align., but do I have to pay much attention to matching dispersion patterns at 400-500hz crossover. The horns will have around 90 deg dispersion at the x-over where the cones will be omni???

(Q 3) And finally center to center spacing - is it supposed to be under 1/2 or 1/4 wavelength?


Any and all suggestions welcome. This system will be overkill, but it is a big room and I want it to be loafing along at reference level for movies.
 
So I'm thinking either a sealed or ported cab with a pair of pro 15" or 18" drivers. Budget is under $300 per driver since I have to buy 12 or 14 of them :eek:. Maybe I should consider singles for the surrounds?


At fist glance, the B&C 15TBW100 looks good in a simple bass reflex cab. Two of them together should give me around 97db/w/m with 3000 watts rms.

Their 18", 18 TBW100 offering looks good too. Higher sensitivity and a stated bandwidth of 35-1Khz.

Will using these 18's compromise sound quality in the 200-500hz range as compared to the 15" drivers?

(Q 2) With the active x-overs it will be easy to time align., but do I have to pay much attention to matching dispersion patterns at 400-500hz crossover. The horns will have around 90 deg dispersion at the x-over where the cones will be omni???

(Q 3) And finally center to center spacing - is it supposed to be under 1/2 or 1/4 wavelength?[/COLOR]

Any and all suggestions welcome. This system will be overkill, but it is a big room and I want it to be loafing along at reference level for movies.
Four Gjallerhorns will be able to do structural damage in a room only 28x38x10.5ft.
A pair of B&C 15TBW100 in a ported cabinet driven with 3000 watts will easily do 125 dB.
12 to 14 of them? With a low 500 Hz crossover, one will keep up with a 288.

The 15 will sound better than the 18 around the crossover region you suggest, and will be closer to 90 degree dispersion, the 18 would be slightly narrower.

If center to center spacing is more than 1/4 wavelength, comb filtering will result.

However, with the system you propose, you would soon be so deaf that you won't notice comb filtering;) .
 

steve71

Member
2007-11-12 6:01 pm
Four Gjallerhorns will be able to do structural damage in a room only 28x38x10.5ft.
A pair of B&C 15TBW100 in a ported cabinet driven with 3000 watts will easily do 125 dB.
12 to 14 of them? With a low 500 Hz crossover, one will keep up with a 288.

The 15 will sound better than the 18 around the crossover region you suggest, and will be closer to 90 degree dispersion, the 18 would be slightly narrower.

If center to center spacing is more than 1/4 wavelength, comb filtering will result.

However, with the system you propose, you would soon be so deaf that you won't notice comb filtering;) .

The building is constructed of steel beams & metal foom, so I don't think I have to worry about structural damage, but I could be wrong? The drywall could be another story :D. I could do two GH's, but four would even out the in room response, no?

The idea of 6 or 7 speakers is only for surround sound for movies. For music, it will just be the LR speakers playing. And I'll be sitting 24-28ft back from the speakers. The building is pretty leaky when it comes to bass I think... it's just drywall insulation and plywood. There will also be lots of room treatments.

1/4 wave length @ 500hz is only 16.5cm. No way to avoid comb filtering then...
 
The building is constructed of steel beams & metal foom, so I don't think I have to worry about structural damage, but I could be wrong? The drywall could be another story :D. I could do two GH's, but four would even out the in room response, no?

The idea of 6 or 7 speakers is only for surround sound for movies. For music, it will just be the LR speakers playing. And I'll be sitting 24-28ft back from the speakers.

1/4 wave length @ 500hz is only 16.5cm. No way to avoid comb filtering then...
In my control room I have heard the walls flapping at the resonant frequency with only around 105 dB output at 16 Hz.
Four Gjallerhorns are capable of 136.3 dB at 16 Hz at one meter. That could separate drywall from stud rather quickly.

Advocates of multiple subs for evening out room response speak in terms of small rooms, where the wavelengths are much longer than room dimensions.
Your room is not small, 35 feet is a 32 Hz wavelength, almost the length of a low B on a bass guitar.

Tom Danley's Synergy type speakers have all the drivers combined on a single constant directivity horn, each within 1/4 wavelength of the adjacent frequency band. No comb filtering, excellent phase, frequency and polar response.
The SH-50 has response low enough to use with the Gjallerhorn. With output capability of around 130 dB, a pair would suffice for a room your size.

Jason Cave has a used pair advertised for $4500 per pair plus shipping, available for pick up or audition in Luray, VA. 540-860-1099.

Art
 
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Surely that's not a regular 4 string?
The lowest note on those would be the open E string at 41Hz.
The bass player for the Red Elvises only uses three strings, but most electric basses are now 5 string.
The change seemed to start happening in the 90s, by the start of this century it seemed about 50%, now I see a lot more 5 strings than 4 strings.

40 Hz response used to be fine for pop, now 30 Hz will get most of it done, though there is plenty of music below that.
 

turbodawg

Member
2004-02-13 12:51 am
Any and all suggestions welcome. This system will be overkill, but it is a big room and I want it to be loafing along at reference level for movies.

Check out this link in regards to placing your subs vs. the room.

Boundary Cancellation and Room Modes

Have you considered a folded front loaded horn of some sort? This seemed like it was kind of close to meeting your needs, maybe redesign a bit smaller with a 15"...?

http://forum.speakerplans.com/topic11659_post369161.html#369161
 
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steve71

Member
2007-11-12 6:01 pm
In my control room I have heard the walls flapping at the resonant frequency with only around 105 dB output at 16 Hz.

For sure, it doesn't take much if you happen to find out the resonant frequency of the drywall.

Tom Danley's Synergy type speakers have all the drivers combined on a single constant directivity horn, each within 1/4 wavelength of the adjacent frequency band. No comb filtering, excellent phase, frequency and polar response.
The SH-50 has response low enough to use with the Gjallerhorn. With output capability of around 130 dB, a pair would suffice for a room your size.

I'm always in awe of what Tom has achieved with the synergy horn. I'd love to hear them one day. But for now, working with what I have, there is no way around the 1/4 wavelength rule given the size of the Altec horns. I guess this is something you just have to accept as a compromise. There seem to be a fair amount of praise for the Onken and the Altec a7 etc and they all break the 1/4 wavelength rule.
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Jason Cave has a used pair advertised for $4500 per pair plus shipping, available for pick up or audition in Luray, VA. 540-860-1099.

Art

I missed that part the first time around. Very tempting, are they the active or passive version? At that price, I guess passive. I really wanted to have identical speakers (or very close) all the way round. Does Danley's smaller horns play down at low as the SH-50?