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-   -   calculating of a BVR-enclosure (http://www.diyaudio.com/forums/full-range/226640-calculating-bvr-enclosure.html)

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 (http://www.diyaudio.com/forums/showthread.php?p=3303978#post3303978)
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 (http://www.diyaudio.com/forums/showthread.php?p=3304458#post3304458)
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 (http://www.diyaudio.com/forums/full-range/226640-calculating-bvr-enclosure-post3303487.html#post3303487)
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 (http://www.diyaudio.com/forums/showthread.php?p=3318379#post3318379)
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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