Would an isobaric subwoofer help lower the bass response? If possible I want to try and avoid a port as they colour the sound somewhat. Would an isobaric enclosure work with an expensive bass driver to air and a cheaper unit behind it, or would it have to be the same unit? Realitically, how much would the different frequency responses matter?
Hi,
Discussing Isobaric in terms of a PA is pointless.
Its is no different to a driver equivalent to the
combined parameters of two PA drivers.
They are not hard to find.
And no you can't use a cheap and expensive
drivers, two cheap would work better, and
isobaric does suit cheap drivers as a scheme.
rgds, sreten.
Discussing Isobaric in terms of a PA is pointless.
Its is no different to a driver equivalent to the
combined parameters of two PA drivers.
They are not hard to find.
And no you can't use a cheap and expensive
drivers, two cheap would work better, and
isobaric does suit cheap drivers as a scheme.
rgds, sreten.
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Do you mean you want a better LF extension.
A good reflex doesn't color the sound, that's a lie. Alignment, speaker, port and driver needs to be seriously calculated/simulated.
If you don't want the monstrous 300L sealed cabinets for good low-end then your only alternative is the reflex. There are no alternatives to the sealed speaker (from what I know). You can always EQ or boost and I'm not sure if that's what you want.
I'd like to point out that ATC use ports on their SCM50.
Ports really aren't a bad thing. They give you a lot of extra output and reduce driver distortion.
+1 to everything Inducor just posted.
A ported (or variant) design with a nice 15" driver a side would be smaller than you initially wanted (2x15", IIRC), go plenty loud enough, and probably low enough.
To check, I recommend you download Audacity (free), and run some music through that you know to have a fairly hefty low end - there's a built-in spectrum analyser. There's so little that goes below 40Hz that, for a PA application, doing so makes very little sense.
To answer your question of how much difference frequency response will actually make, I simulated a 70L closed box with the Beyma 15" driver I mentioned earlier.
Driven to its not-inconsiderable Xmax (9.5mm one-way), it'll do 112dB at 40Hz. Keeping Xmax at 40Hz, it'll do 121dB at 100Hz.
My 120L TQWT (or whatever it is - I'll start a thread soon), gives 124dB@40Hz, 127dB@100Hz. Still within Xmax.
You could run the TQWT at 1/10th power of the sealed box, and it'll still be louder at the bottom end. 100w on one, 1000w on the other, and the lower power one will still be doing more at 40Hz.
Trust me, you don't want to go sealed.
Chris
Ports really aren't a bad thing. They give you a lot of extra output and reduce driver distortion.
+1 to everything Inducor just posted.
A ported (or variant) design with a nice 15" driver a side would be smaller than you initially wanted (2x15", IIRC), go plenty loud enough, and probably low enough.
To check, I recommend you download Audacity (free), and run some music through that you know to have a fairly hefty low end - there's a built-in spectrum analyser. There's so little that goes below 40Hz that, for a PA application, doing so makes very little sense.
To answer your question of how much difference frequency response will actually make, I simulated a 70L closed box with the Beyma 15" driver I mentioned earlier.
Driven to its not-inconsiderable Xmax (9.5mm one-way), it'll do 112dB at 40Hz. Keeping Xmax at 40Hz, it'll do 121dB at 100Hz.
My 120L TQWT (or whatever it is - I'll start a thread soon), gives 124dB@40Hz, 127dB@100Hz. Still within Xmax.
You could run the TQWT at 1/10th power of the sealed box, and it'll still be louder at the bottom end. 100w on one, 1000w on the other, and the lower power one will still be doing more at 40Hz.
Trust me, you don't want to go sealed.
Chris
If it'd been anything other than electronic music I'd agree that there is hardly anything going on below 40Hz but with electronic you cannot be sure at all.
I've seen a number of PA subs go up in smoke due to excessive very low frequencies from some electronic music.
Problem is drivers suitable for PA work which can do those frequencies are very few and far between. The only one I can think of at the moment is the BMS 18N862.
Overview
No idea if it is available stateside but if it is it won't be cheap.
In the UK it costs £610 plus VAT.
I've seen a number of PA subs go up in smoke due to excessive very low frequencies from some electronic music.
Problem is drivers suitable for PA work which can do those frequencies are very few and far between. The only one I can think of at the moment is the BMS 18N862.
Overview
No idea if it is available stateside but if it is it won't be cheap.
In the UK it costs £610 plus VAT.
Hi lejockey,
Just sitting here on the side lines recuperating from an operation, and saw your thread, anyway, I still don't know what you really want to do, but:
If you are wanting to fill in below the ATC SCM50's -6dB point of 38Hz (79dB?) maybe a transmission line might work for you. I have played around w/ the driver suggested by sreten in Post #8 in Hornresp quite a bit (obviously, sreten's solution would work).
Here is a tapered transmission line (TTL) that would provide you with below 38Hz extension. The mouth is set to the equivalent of a 6"Dia. duct, I pushed the fb down to the bottom of the usage range to reduce bottom end displacement (but this is just a suggested starting point). You can fiddle around w/ this in Hornresp to push the response to a higher frequency, and reduce the volume. A little damping material is added in Hornresp (it may simulate the internal losses). It's a very simple build if you go w/ the single fold method, and should still be portable.
One box should do it per SCM50, want more SPL use more boxes. Inexpensive driver, easy build....
Regards,
Just sitting here on the side lines recuperating from an operation, and saw your thread, anyway, I still don't know what you really want to do, but:
If you are wanting to fill in below the ATC SCM50's -6dB point of 38Hz (79dB?) maybe a transmission line might work for you. I have played around w/ the driver suggested by sreten in Post #8 in Hornresp quite a bit (obviously, sreten's solution would work).
Here is a tapered transmission line (TTL) that would provide you with below 38Hz extension. The mouth is set to the equivalent of a 6"Dia. duct, I pushed the fb down to the bottom of the usage range to reduce bottom end displacement (but this is just a suggested starting point). You can fiddle around w/ this in Hornresp to push the response to a higher frequency, and reduce the volume. A little damping material is added in Hornresp (it may simulate the internal losses). It's a very simple build if you go w/ the single fold method, and should still be portable.
One box should do it per SCM50, want more SPL use more boxes.
Inexpensive driver, easy build....Regards,
Attachments
I would point you to the Rythmik Audio servo subwoofers. If you want to go dual, there are three options:
Rythmik Audio DS1500 CI - 15" Direct Servo subwoofer (see bottom of page for Dual driver CI option)
Rythmik Audio DS1200 CI - 12" Direct Servo subwoofer (see bottom of page for Dual driver CI option)
Rythmik Audio GR Custom Install - 12" Direct Servo subwoofer using GR Research drivers (see bottom of page for Dual driver CI option)
These all have very low distortion, which is what I think will sound best with the ATC speakers you have. Just my $0.02.
Enjoy,
Deon
Rythmik Audio DS1500 CI - 15" Direct Servo subwoofer (see bottom of page for Dual driver CI option)
Rythmik Audio DS1200 CI - 12" Direct Servo subwoofer (see bottom of page for Dual driver CI option)
Rythmik Audio GR Custom Install - 12" Direct Servo subwoofer using GR Research drivers (see bottom of page for Dual driver CI option)
These all have very low distortion, which is what I think will sound best with the ATC speakers you have. Just my $0.02.
Enjoy,
Deon
I guess that you need an answer here. A push-pull isobaric would lower the LF extension, yes, because of the added air mass to the 2x drivers used in the enclosure.
Another rec. for Rythmik
As the owner of a DS1500 - I would absolutely second Deon's point - the Rythmik Audio product is as good as it gets. For more fidelity, add several of them to ameliorate room modes - bonus, you reduce excursion (and therefore distortion) by having more of them.
Cheers,
-Tal
As the owner of a DS1500 - I would absolutely second Deon's point - the Rythmik Audio product is as good as it gets. For more fidelity, add several of them to ameliorate room modes - bonus, you reduce excursion (and therefore distortion) by having more of them.
Cheers,
-Tal
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