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-   -   Why no high efficiency bass drivers for sealed bass channel? (http://www.diyaudio.com/forums/multi-way/175009-why-no-high-efficiency-bass-drivers-sealed-bass-channel.html)

hasselbaink 8th October 2010 07:56 AM

Why no high efficiency bass drivers for sealed bass channel?
 
This is how it stands: Many, many audiophiles promote the use of sealed enclosures to produce bass sound, and while I am not into arguing the merits of one type of box vs. another type, the sealed enclosure does hold some desireable properties.

HOWEVER - despite of this there are not many options for us who seek high efficiency woofers for the sealed topology! Why is this? Maybe it is because most pro format drivers are made for the PA market and ported boxes. Maybe the hifi home audio manufacturers have withdrawn from the large format woofer market.

What I would like to see are more 12" and 15" woofers made for the sealed topology. Preferably 16 ohm so that they can be paralleled for more efficiency.

Suggestions for 12" or 15" hi-eff. woofers for a sealed 30 - 150 hz channel are much appreaciated.

Sincerely
Kris

Kjeldsen 8th October 2010 08:17 AM

high efficiency woofers are always efficient above 100 Hz. The only way I know of, to get high eff in low freq, is massive cone area. Like the fostex 30" or multiple 12 to 15". Another way is large horns, but that's no what you asked for.

Try comparing a 15" pro speaker like Beyma and JBL. They could be rated 97 dB, but below 100 Hz. they are only 90 dB and at 30 Hz typical 85 dB.

You should go for low freq woofers designed for large cabinets (high Vas), since they will, in real life, produce deep bass with the highest eff. possible But don't expect anything above 90 dB.

Kjeldsen 8th October 2010 08:23 AM

My suggestion (if it's still available)

http://www.d-s-t.com.au/data/Peerless/831857.pdf

Two of these per side, should give a fairly good efficiency, even below 30 Hz. But they will be the size of a closet.

CLS 8th October 2010 08:43 AM

Some factors just don't come together.

To get high efficiency, you'd need light cone & big motor, than you end up with a low Q driver with high fs, which is no bass.

To keep the above and make the fs lower and Vas high, you'd need super soft suspension which is not easy to maintain consistence, in both manufacturing and operation of the driver itself. (and even then, the Qts is still low, it's dominated by the motor)

If you manage to get all the above, than at the operation of high excursion at low fs, your light cone and super soft suspension might probably deform too much or even flapping around. (the high pressure of a sealed box is not even added to the picture)

Let's see the new woofers of those mainstream pro sound brands, the cones tend to be heavier and heavier. Because they need to lower the Vas to make the cabinet small. Thick and heavy cones survive the high power (excursion) torture better than light cones, and power is the easy part. So they just go this way.

Unless we have a super light and rigid material (let's say 24" cone of under 100g, for ex.), we can never escape the circle.

StigErik 8th October 2010 09:07 AM

You might actually end up with better efficiency using very large and extremely high sensitivity woofers in open baffle (with EQ) instead of typical "hifi" drivers intended for sealed box. As an example my own dual 21" H-baffle sub's are close to 100 dB sensitive (2.83V / 2W into 4 ohms) at 20 Hz. Admittedly, the boxes (or baffles) required are quite large.... :D

In my opinion, open baffle offers a bass quality that cannot be matched.

Inductor 8th October 2010 09:46 AM

https://www.madisound.com/store/prod...oducts_id=8304
Suggested Alignments:
Sealed box of 2.6 cubic feet for and F3 of 38Hz
http://www.zaphaudio.com/SB12.3/
Would a Fostex work in a closed box?
https://www.madisound.com/store/prod...oducts_id=8676

hasselbaink 8th October 2010 09:56 AM

Kjeldsen and CLS -> your replies are well appreaciated.

I was careful not to ask for subwoofer drivers and only for 30 - 150 capable drivers.
The issue with motor strength, mms, Fs and Q is of course a framework we have to work within. And there have been drivers before that were high(ish) sensitivity and would work in a sealed box such as Beyma 15B100R which would give adequate output to 30 Hz with a bit of room gain.

Still, the white elephant would be a 16 ohm woofer with 92+ sensitivity that would be suited to sealed box implementation. In parallel such a beast would be able to take the strain off my actively crossed all tube amplifier playback system.

Kris

Kjeldsen 8th October 2010 10:15 AM

I bet the Beyma 15B100R will not give more output below 100 Hz., than the Peerless I mentioned. But (there's always a but), the energy needed at real low freq. are not so demanding as from 100-200 Hz., so the Beyma will gain here - but eq. or roomgain are needed to smothend out the freq. response.

Since you're from Denmark, why not just call flex units and have two 15" custom made.

hasselbaink 8th October 2010 10:40 AM

Quote:

Originally Posted by Inductor (Post 2326193)
https://www.madisound.com/store/prod...oducts_id=8304
Suggested Alignments:
Sealed box of 2.6 cubic feet for and F3 of 38Hz
Zaph|Audio - SB12.3 3-Way Tower
Would a Fostex work in a closed box?
https://www.madisound.com/store/prod...oducts_id=8676

I might be tempted to put two of those in series to raise Z, but it would do nothing for efficiency.

The Fostex is not a sealed box driver, sorry.

hasselbaink 8th October 2010 10:48 AM

Open Baffle
 
Quote:

Originally Posted by StigErik (Post 2326171)
You might actually end up with better efficiency using very large and extremely high sensitivity woofers in open baffle (with EQ) instead of typical "hifi" drivers intended for sealed box. As an example my own dual 21" H-baffle sub's are close to 100 dB sensitive (2.83V / 2W into 4 ohms) at 20 Hz. Admittedly, the boxes (or baffles) required are quite large.... :D

In my opinion, open baffle offers a bass quality that cannot be matched.

We cannot even begin to discuss open baffle and its limitations pertaining to sound. Suffice it to say that I am familiar with open baffle and I use it in very specific manner in the midrange.

I do run my speakers actively but with pure tube amplification only. In a sense I do use EQ since I cross well below target XO point in order to raise sub 100 Hz output. In a way this is a nonconformist setup since I think bass sounds more real with tube amps than with solid state. Most audiophiles disagree - their loss.

Best
Kris


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