Hello,
I have some older Chase VS 18.1 subwoofers in my theater, 4 total and I am looking to replace the drivers with something that digs a bit deeper with lower distortion. I am a bit surprised that at times they can sound a bit boomy. I don't think the amplifier would be the culprit. The amp is a Crown Macrotech 3600VZ, damping factor is greater than 1000 at 400hz. It could be placement which is in the from left corner co-located but I am thinking it's actually the drivers themselves.
The current drivers, I've linked to below are made by Eminence
https://data-bass.com/drivers/5bef3fc0b666190004d5d41e
The drivers I am considering are the Dayton Ultimax and the Stereo Integrity HT 18.
https://www.parts-express.com/Dayto...C-Subwoofer-2-Ohm-Per-Coil-295-718?quantity=1
https://stereointegrity.com/product/ht-18-v3/
The sub boxes are about 8.5ft3 net tuned to 19hz.
The Eminence drivers have a super low QTS of ,245
The Dayton Ultimax 18 is listed at .53 QTS and the SI HT 18, .59 QTS
I do not care for boomy bass but as it a theater with ported subs, I guess I may get boom whether I want it or not. I am concerned that the QTS specs of both drivers I'm looking at may not give me the sound quality I'm looking for. I guess it sounds like I want my cake and to eat it, too.
I am not concerned that the Ultimax is more expensive and I have to admit the carbon fiber cone is good looking. Stereo Integrity has always been great bang for the buck though. Which sub would you choose and why? Thanks in advance for your help!
I have some older Chase VS 18.1 subwoofers in my theater, 4 total and I am looking to replace the drivers with something that digs a bit deeper with lower distortion. I am a bit surprised that at times they can sound a bit boomy. I don't think the amplifier would be the culprit. The amp is a Crown Macrotech 3600VZ, damping factor is greater than 1000 at 400hz. It could be placement which is in the from left corner co-located but I am thinking it's actually the drivers themselves.
The current drivers, I've linked to below are made by Eminence
https://data-bass.com/drivers/5bef3fc0b666190004d5d41e
The drivers I am considering are the Dayton Ultimax and the Stereo Integrity HT 18.
https://www.parts-express.com/Dayto...C-Subwoofer-2-Ohm-Per-Coil-295-718?quantity=1
https://stereointegrity.com/product/ht-18-v3/
The sub boxes are about 8.5ft3 net tuned to 19hz.
The Eminence drivers have a super low QTS of ,245
The Dayton Ultimax 18 is listed at .53 QTS and the SI HT 18, .59 QTS
I do not care for boomy bass but as it a theater with ported subs, I guess I may get boom whether I want it or not. I am concerned that the QTS specs of both drivers I'm looking at may not give me the sound quality I'm looking for. I guess it sounds like I want my cake and to eat it, too.
I am not concerned that the Ultimax is more expensive and I have to admit the carbon fiber cone is good looking. Stereo Integrity has always been great bang for the buck though. Which sub would you choose and why? Thanks in advance for your help!
T/S max flat alignment:
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3 = 188.42 L/6.654 ft^3 net using Qes to account for some Vc heating, raising Qts, so yours are technically too big = sometimes 'boomy'
(Ft^3 = (Vb)/~28.31685)
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
F3 (Hz) = Fs*0.28*Qts'^-1.4
(Qts'): (Qts) + any added series resistance (Rs):
https://web.archive.org/web/20220707003028/http://www.mh-audio.nl/Calculators/newqts.html
You don't have to accept 'boom' in ported cabs, just critically damp them.
Regardless, yours are extremely over damped, though theater acoustics should be raising its low end somewhat to further promote possible 'boominess', ergo going with higher Qts/bigger boxed drivers will just make matters worse.
So reduce the net Vb, re-tune vent to 'taste' and if still a bit 'boomy', do the 'click' test or impulse response if using a proper measurement system; or maybe best overall to build tapped TL or horn (Bp6) cabs with existing drivers if space allows.
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3 = 188.42 L/6.654 ft^3 net using Qes to account for some Vc heating, raising Qts, so yours are technically too big = sometimes 'boomy'
(Ft^3 = (Vb)/~28.31685)
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
F3 (Hz) = Fs*0.28*Qts'^-1.4
(Qts'): (Qts) + any added series resistance (Rs):
https://web.archive.org/web/20220707003028/http://www.mh-audio.nl/Calculators/newqts.html
You don't have to accept 'boom' in ported cabs, just critically damp them.
Regardless, yours are extremely over damped, though theater acoustics should be raising its low end somewhat to further promote possible 'boominess', ergo going with higher Qts/bigger boxed drivers will just make matters worse.
So reduce the net Vb, re-tune vent to 'taste' and if still a bit 'boomy', do the 'click' test or impulse response if using a proper measurement system; or maybe best overall to build tapped TL or horn (Bp6) cabs with existing drivers if space allows.
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Hi GM,
Thanks so much for you detailed reply. If I am interpreting your response correctly, the boxes are too big for the current drivers and I need to reduce box volume by about 2 cubic feet? If I take up that much volume in the cabinet, I think that would result in much higher tuning
I am a bit confused by the termed overdamped. Doesn't that normally result in tight bass, not boomy, or do I have that incorrect? Would the two drivers I am considering exacerbate this problem with their higher QTS specs?
Thanks so much for you detailed reply. If I am interpreting your response correctly, the boxes are too big for the current drivers and I need to reduce box volume by about 2 cubic feet? If I take up that much volume in the cabinet, I think that would result in much higher tuning
I am a bit confused by the termed overdamped. Doesn't that normally result in tight bass, not boomy, or do I have that incorrect? Would the two drivers I am considering exacerbate this problem with their higher QTS specs?
Greets!
You're welcome!
When the box is too big for a given tuning the driver rolls off at a higher than optimum frequency, ergo over damped and in your case its super low Qt makes it even worse, but make it too small, creating a hump in the response = under damped.
Using the simplified sealed box chart, the 0.7 is max flat/critically damped, so 0.5 is over damped and the rest are increasingly under damped.
Use the formulas to see how well other drivers perform in your box by comparing how close to their max flat alignment matches your box's net Vb with +10 % being 'close enough' and your call WRT to how close to Fb is acceptable.
You're welcome!
When the box is too big for a given tuning the driver rolls off at a higher than optimum frequency, ergo over damped and in your case its super low Qt makes it even worse, but make it too small, creating a hump in the response = under damped.
Using the simplified sealed box chart, the 0.7 is max flat/critically damped, so 0.5 is over damped and the rest are increasingly under damped.
Use the formulas to see how well other drivers perform in your box by comparing how close to their max flat alignment matches your box's net Vb with +10 % being 'close enough' and your call WRT to how close to Fb is acceptable.
