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Sergii 29th December 2012 08:29 PM

calculating of a BVR-enclosure
 
4 Attachment(s)
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.

GM 30th December 2012 07:06 AM

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

Sergii 30th December 2012 09:41 AM

5 Attachment(s)
Quote:

Originally Posted by GM (Post 3303978)
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?

GM 30th December 2012 04:31 PM

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

Sergii 30th December 2012 08:27 PM

2 Attachment(s)
Quote:

Originally Posted by GM (Post 3304458)
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?

GM 30th December 2012 10:06 PM

2 Attachment(s)
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

Sergii 31st December 2012 12:50 PM

Dear GM, many thanks.

Happy New Year!!!

to be continued 2013

with best regards

Sergii
Kiev

Sergii 9th January 2013 07:04 PM

3 Attachment(s)
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.

sreten 9th January 2013 07:44 PM

Quote:

Originally Posted by Sergii (Post 3303487)
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.

Sergii 10th January 2013 12:04 PM

Quote:

Originally Posted by sreten (Post 3318379)
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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