Simple question:
When you load two drivers in a clamshell configuration and wire them in series (out of phase) what is your net SPL (Woofer #1 SPL + woofer #2 SPL) as compared to the native efficiency of ONE driver? Is it -3 Db, -6 Db, or -0 Db?
Recap:
If I load two woofers with a native efficiency rating of 90 Db SPL each in a clamshell configuration, out of phase, wired in series, what is my net loss in efficiency?
Thanks,
-fortyquid
When you load two drivers in a clamshell configuration and wire them in series (out of phase) what is your net SPL (Woofer #1 SPL + woofer #2 SPL) as compared to the native efficiency of ONE driver? Is it -3 Db, -6 Db, or -0 Db?
Recap:
If I load two woofers with a native efficiency rating of 90 Db SPL each in a clamshell configuration, out of phase, wired in series, what is my net loss in efficiency?
Thanks,
-fortyquid
Wired in parallel : 90 dB, no loss compared to single driver and half the enclosure size.
Wired in series : 84 dB, 6 dB down compared to single driver and half the enclosure size. Not sure why anybody would want to wire drivers in series in an isobaric design.
Wired in series : 84 dB, 6 dB down compared to single driver and half the enclosure size. Not sure why anybody would want to wire drivers in series in an isobaric design.
Yes, precisely. I have all these nice little 4Znom Peerless 830413 5.25" midwoofers that my Pioneer VSX D-411 isn't rated for. I don't particularly want to have to build an enclosure (actually five enclosures) twice as large with two woofers MTM; besides, I only have eight, and they're no longer on the market. So I suppose I will just have to keep the pot. down a bit. As efficient as these drivers are, I don't really need 500W anyway.
By the way, is that last idea kosher? Somebody at Parts Express tech. support told me I could probably get away with it if I didn't push the reciever too hard, say 6Db down, but they have been wrong before...
MJK, is it possible to implement your mathcad spreadsheets without a Bl spec. for the driver?
Thanks,
-fortyquid
By the way, is that last idea kosher? Somebody at Parts Express tech. support told me I could probably get away with it if I didn't push the reciever too hard, say 6Db down, but they have been wrong before...
MJK, is it possible to implement your mathcad spreadsheets without a Bl spec. for the driver?
Thanks,
-fortyquid
No, you need to enter a value for the driver's BL.
The MathCad Isobaric worksheets assume a parallel connection of the drivers. Modeling a series connection would be tricky in this worksheet, but I guess you could get a good estimate of the enclosure geometry and the potential response shape.
You can calculate it:
Cms = Vas/(Sd^2*rho*c^2)
where:
Vas is in m^3 (liters*0.001)
Sd is in cm^2
c is in meters/sec*0.0001 to get Cms in mm/N
then:
Mms = 1/[(2*pi*Fs)^2*Cms]
BL = [(2*Pi*Fs*Re*Mms)/Qes]^0.5
Example:
B*L (N/A) = 4.3729
Cms (mm/N) = 1.3479E-03
Mms (Kg) = 0.004448
Sd = 57.010
Vas = 6.200
Fs = 65.000
Re = 6.000
Qes = 0.570
p0 = 1.210
c = 342.000
GM
Cms = Vas/(Sd^2*rho*c^2)
where:
Vas is in m^3 (liters*0.001)
Sd is in cm^2
c is in meters/sec*0.0001 to get Cms in mm/N
then:
Mms = 1/[(2*pi*Fs)^2*Cms]
BL = [(2*Pi*Fs*Re*Mms)/Qes]^0.5
Example:
B*L (N/A) = 4.3729
Cms (mm/N) = 1.3479E-03
Mms (Kg) = 0.004448
Sd = 57.010
Vas = 6.200
Fs = 65.000
Re = 6.000
Qes = 0.570
p0 = 1.210
c = 342.000
GM
Do all isobaric enclosures mean half the size? Half the size of Vb if one driver is used or, if two drivers are used? What are your comments on the sound of an isobaric enclosure?
Two isobaricly aligned drivers will have a combined Vas. equal to half that of a single driver; i.e., will need a box of half the volume of the single driver box.
So Isobaric = 1/2 the volume, 1/4 the Spl ( 1/2Vas+ 2Z =-6 Db) if wired in series , or 1/2 the Spl (1/2Vas+ 1/2Z= -3 Db), and twice the power handling capacity.
So you're right back where you started from, with a smaller box and larger amp.
-fortyquid
So Isobaric = 1/2 the volume, 1/4 the Spl ( 1/2Vas+ 2Z =-6 Db) if wired in series , or 1/2 the Spl (1/2Vas+ 1/2Z= -3 Db), and twice the power handling capacity.
So you're right back where you started from, with a smaller box and larger amp.
-fortyquid
Also remember that in clamshell configuration, the drivers will not put out pretty much anything above a couple hundred Hz.
>What are your comments on the sound of an isobaric enclosure?
====
In the sub/bass BW, no different than a single driver in a 2x larger cab. As Dan noted, in clamshell config they begin cancelling each other out pretty quick, so for wide BW use must be in tandem.
====
>So you're right back where you started from, with a smaller box...
====
And unless the drivers normally require a huge cab, it's not that much smaller when you consider the driver 'hanging in the breeze'.
GM
====
In the sub/bass BW, no different than a single driver in a 2x larger cab. As Dan noted, in clamshell config they begin cancelling each other out pretty quick, so for wide BW use must be in tandem.
====
>So you're right back where you started from, with a smaller box...
====
And unless the drivers normally require a huge cab, it's not that much smaller when you consider the driver 'hanging in the breeze'.
GM
But if you're into bandpass systems, it's wonderful.
Speaking of which.....
I've been using a 6obp woofer system for the last year or so. I was attracted to the design by the prospect of getting 26Hz at 110 db from a 5 1/4" driver, and pretty good transients too, I figured, because of the small Sd.
Can somebody tell me what kind of improvement I'm looking at if I switch over to TL? In other words, why is everyone so down on BPs? I haven't done any extensive listening tests on other configurations with similar bandwidth, so I really don't have anything to campare them with, but I know Bose uses the configuration with his Lifestyle subsat systems, so I figure it should sound allright, and my personal experience corrolates, limitted though it is.
What gives? What's the big problem with Bandpass?
Speaking of which.....
I've been using a 6obp woofer system for the last year or so. I was attracted to the design by the prospect of getting 26Hz at 110 db from a 5 1/4" driver, and pretty good transients too, I figured, because of the small Sd.
Can somebody tell me what kind of improvement I'm looking at if I switch over to TL? In other words, why is everyone so down on BPs? I haven't done any extensive listening tests on other configurations with similar bandwidth, so I really don't have anything to campare them with, but I know Bose uses the configuration with his Lifestyle subsat systems, so I figure it should sound allright, and my personal experience corrolates, limitted though it is.
What gives? What's the big problem with Bandpass?
>I was attracted to the design by the prospect of getting 26Hz at 110 db from a 5 1/4" driver, and pretty good transients too, I figured, because of the small Sd.
====
But did you achieve it, and over how wide a BW?
====
>Can somebody tell me what kind of improvement I'm looking at if I switch over to TL? In other words, why is everyone so down on BPs?
====
Poor transient response (much more group delay), even compared to a BR. They ring like a bell unless damped by a horn. That said, if it's limited to sub duty, then due to our poor hearing acuity down low, the group delay decays enough that it's inaudible by the time it gets up to a frequency where it can be sensed.
A sealed, TL, extreme EBS, and especially a horn, has a much 'tighter'/accurate LF response, and the wider the dynamic range/efficiency desired, the more critical 'clean' becomes.
====
>I haven't done any extensive listening tests on other configurations with similar bandwidth, so I really don't have anything to campare them with, but I know Bose uses the configuration with his Lifestyle subsat systems, so I figure it should sound allright, and my personal experience corrolates, limitted though it is. What gives? What's the big problem with Bandpass?
====
Among folks into high performance audio, B*** is a derogatory four letter word WRT business ethics/performance, so if you consider them adequate/good performers, probably any designs discussed here will be way beyond your expectations. Then again, I've known folks who preferred a lot of coloration (highly resonant) in their systems rather than accurately reproducing the signal, so as always, YMMV.
GM
====
But did you achieve it, and over how wide a BW?
====
>Can somebody tell me what kind of improvement I'm looking at if I switch over to TL? In other words, why is everyone so down on BPs?
====
Poor transient response (much more group delay), even compared to a BR. They ring like a bell unless damped by a horn. That said, if it's limited to sub duty, then due to our poor hearing acuity down low, the group delay decays enough that it's inaudible by the time it gets up to a frequency where it can be sensed.
A sealed, TL, extreme EBS, and especially a horn, has a much 'tighter'/accurate LF response, and the wider the dynamic range/efficiency desired, the more critical 'clean' becomes.
====
>I haven't done any extensive listening tests on other configurations with similar bandwidth, so I really don't have anything to campare them with, but I know Bose uses the configuration with his Lifestyle subsat systems, so I figure it should sound allright, and my personal experience corrolates, limitted though it is. What gives? What's the big problem with Bandpass?
====
Among folks into high performance audio, B*** is a derogatory four letter word WRT business ethics/performance, so if you consider them adequate/good performers, probably any designs discussed here will be way beyond your expectations. Then again, I've known folks who preferred a lot of coloration (highly resonant) in their systems rather than accurately reproducing the signal, so as always, YMMV.
GM
Has anyone tried a small bookshelf speaker instead of a sub with an isobaric design. I believe Totem makes a speaker like this and the idea intrigued me.
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