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Old 29th December 2012, 08:29 PM   #1
Sergii is offline Sergii  Ukraine
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Default calculating of a BVR-enclosure

Hi,

Inspired by WHT-acoustic model PR4 I try to calculate a bass-section for bilding an BVR-enclosure: Full range+bass-section. My bass-driver has very suitable data for BR but this kind of enclosure I am not interested in because of heavy and slow bass. Love horn bass, but dimensions for one with 12" driver would be very huge.
Below I post some simulation in hornresp.
T/S-data for Bass-driver:
Fs 33Hz
Vas 248 L
Sd 464 cm2
Qts 0,383
Mms 27,67 g
Le 0,8mH
Bl 9,6


My questions would be:
1. If the T/S parameters are well suitable for this enclosure? According to the simulated data I have Fb 36 Hz (-6dB) with group delay below 11ms.
2. Are these good data for this kind of enclosure I can get?
3. As alternative enclosure I can build e small sized BR tuned a little higher then Fs of the driver. In my case 36 Hz.


Please give some comment.
Attached Images
File Type: jpg input parameters.jpg (139.2 KB, 224 views)
File Type: jpg SPL Response.jpg (103.5 KB, 220 views)
File Type: jpg group delay.jpg (106.4 KB, 217 views)
File Type: jpg schematic diagramm.jpg (68.8 KB, 216 views)

Last edited by Sergii; 29th December 2012 at 08:43 PM.
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Old 30th December 2012, 07:06 AM   #2
GM is offline GM  United States
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No, you inputted the T/S specs wrong [Cms, Mmd], plus the response is just for the vent, so use the 'combined response' in TOOLs to see the speaker response.

If you want a prosound 'scoop bin' type of response, then you're close, otherwise tuning it for a bit less mid-bass gain and extending the 'bump' higher in frequency will typically work better in a HIFI app.

GM
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Old 30th December 2012, 09:41 AM   #3
Sergii is offline Sergii  Ukraine
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Quote:
Originally Posted by GM View Post
No, you inputted the T/S specs wrong [Cms, Mmd], plus the response is just for the vent, so use the 'combined response' in TOOLs to see the speaker response.

If you want a prosound 'scoop bin' type of response, then you're close, otherwise tuning it for a bit less mid-bass gain and extending the 'bump' higher in frequency will typically work better in a HIFI app.

GM
Hi GM

I cheked the T/S specs of my driver (Cms = 0,8112 mm/N and Mmd = 22,93 g), these are correct. May be I did not understand you what do you mean.

Just corrected some input par. and I think I am close to the wanted simulation. Have some doubt about a peak apr. 163 Hz very close to the main response of a bass-driver. Can I turn off this peak with a damping material without making the bass viscous?
Attached Images
File Type: jpg input paramenters.jpg (132.3 KB, 192 views)
File Type: jpg SPL response.jpg (111.6 KB, 29 views)
File Type: jpg group delay.jpg (106.1 KB, 20 views)
File Type: jpg diaphragm displacement.jpg (92.4 KB, 6 views)
File Type: jpg phase response.jpg (147.8 KB, 6 views)
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Old 30th December 2012, 04:31 PM   #4
GM is offline GM  United States
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OK, then double click on 'Sd', then 'yes' to see the way off specs HR is using.

Normal damping of the cab will flatten high Q peaks, dips and overall response can be fine tuned by damping the vent/horn's throat and/or its terminus perimeter to damp down its eigenmodes.

GM
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Old 30th December 2012, 08:27 PM   #5
Sergii is offline Sergii  Ukraine
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Quote:
Originally Posted by GM View Post
OK, then double click on 'Sd', then 'yes' to see the way off specs HR is using.

Normal damping of the cab will flatten high Q peaks, dips and overall response can be fine tuned by damping the vent/horn's throat and/or its terminus perimeter to damp down its eigenmodes.

GM
Yes, It was wrong - the Cms.
Now, I have very different situation. My JBL-simulation in BR-enclosure with vent gives the same thing like in hornresp with the scoop. May be this driver does not suit for BVR?
Attached Images
File Type: jpg group delay.jpg (111.8 KB, 11 views)
File Type: jpg JBL for BR.jpg (217.4 KB, 21 views)
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Old 30th December 2012, 10:06 PM   #6
GM is offline GM  United States
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I don't follow. For one, I get a quite different combined response from your latest ones, though it's very close to the one I calculated initially except mine is a little larger at 143.736 L.

Yours has a better group delay down low, but that's because the 'horn' is a bit too small.

Attached is mine with what I get for your design in shadow:

GM
Attached Images
File Type: gif SCS-300 woofer BVR comparison.gif (12.7 KB, 37 views)
File Type: gif SCS-300 woofer BVR group delay comparison.gif (12.5 KB, 34 views)
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Old 31st December 2012, 12:50 PM   #7
Sergii is offline Sergii  Ukraine
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Dear GM, many thanks.

Happy New Year!!!

to be continued 2013

with best regards

Sergii
Kiev
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Old 9th January 2013, 07:04 PM   #8
Sergii is offline Sergii  Ukraine
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A new try. BVR for bass-section (cut off 290 Hz).
The same in BR-enclosure pipe ported.

Honest I do not see any benefits of BVR.
The full range driver has average sensivity 93 db. Up 2 kHz till 12 kHz 95-96 dB.
Should I build the normal BR or BVR?

I`ve simulate also another driver with low Qts for (BLH-enclosures) which do not work in any BR-enclosures. So I `ve got an interesting result.
Attached Images
File Type: jpg SPL 12` (110 L).jpg (118.3 KB, 23 views)
File Type: jpg group delay 12` (110 L).jpg (115.3 KB, 18 views)
File Type: jpg BR (12` 115 L).jpg (606.7 KB, 15 views)
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Old 9th January 2013, 07:44 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Sergii View Post
Hi,
My bass-driver has very suitable data for BR but this kind of
enclosure I am not interested in because of heavy and slow bass.
T/S-data for Bass-driver:
Fs 33Hz
Vas 248 L
Sd 464 cm2
Qts 0,383
Mms 27,67 g
Le 0,8mH
Bl 9,6

Please give some comment.
Hi,

Sealed is 120L for Q=0.7, classic vented 240L tuned to 33Hz.

Nothing heavy and slow about 240L tuned to 22Hz.
Quasi first order roll-off and -10dB at 20Hz.

Both sealed and vented are about -18dB at 20Hz.

rgds, sreten.

300L and 20Hz tuning, 200L and 24Hz, are also options.
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Last edited by sreten; 9th January 2013 at 07:52 PM.
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Old 10th January 2013, 12:04 PM   #10
Sergii is offline Sergii  Ukraine
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Quote:
Originally Posted by sreten View Post
Hi,
Sealed is 120L for Q=0.7, classic vented 240L tuned to 33Hz.
Nothing heavy and slow about 240L tuned to 22Hz.
Quasi first order roll-off and -10dB at 20Hz.
Both sealed and vented are about -18dB at 20Hz.
rgds, sreten.
300L and 20Hz tuning, 200L and 24Hz, are also options.
O.K. Thank you. But what about a monstrous group delay? I simulated a ported box with volume 240 L - the GD was above 22 mc. Some guy built the recomended enclosure for this bass-driver (specs. very similar to the a.m.) - appr. 145 L and was little disappointed about slow bass. I asked him, what would he do now after getting this experience - he said he would build smaller enclosure 115 Liter with higher tuning.

My intension was to find another enclosure for this driver with a faster sound. I was in hope that BVR would be the one.

Another possible problem with very low tuned enclosure is the room instalation.

May be it is also a question of our taste?
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