Isobarik or compound loading help

[andrew levy]

Hi,

I was wondering if anyone in the forum has hands on experience with isobarik loading. I am building a 3 way with a Dynaudio 30W-100. This driver calls for a very large box, I happen to have 2 extra ones, and thought I could use them in an isobarik configuration and reduce the box size by half.
Aside from the benefit or reduced box volume, I wonder if any of you know of and have heard any audiible improvements by using this configuration. I know a few very credible manufacturers have used this arrangement and wonder if there are any sonic merits to this approach.

Regards,

Andrew

[Daryl]

Four rare and expensive no-longer available drivers, "just lying around".

Yikes.

Isobarik's are an ungainly proposition.

A third-order-sealed alignment can achieve the same bass extension as a second-order-sealed alignment in less than half the enclosure volume.

To implement this you model an enclosure with Qtc=1 then place a capacitor in series which knocks the peak above Ftc flat and extends bass response 1/2 octave below Ftc by resonating with enclosure and driver compliance.

[vasyachkin]

sell the drivers

seriously ...

[spock]

Isobariks should not be used in Hi-fi.

I suggest you sell the dynaudios on ebay, take that $$ and get yourself a driver that will fit in a box size your happy with.

Dynaudio isnt the best at making large woofers anyhow.

[spock]

A capacitor in series, will ruin any woofer. I would not go that way.

[Daryl]

Spock,

I'm not shure what makes you think your an expert but your comments thus far reveal that you haven't yet begun the journey.

The fact that you think you are an expert and qualified to teach others makes you look foolish.

Learn first teach later.

[spock]

Daryl, ive been designing loudspeaker drivers for over 20 years for over a hand full of companies. I would say that gives me some experience in the field.
You really should take your own advice, it will get you a lot farther in life.

Why dont you try and give some useful advice for a change instead of coming on here and making stupid comments regarding other peoples advice.

[Daryl]

"ive been designing loudspeaker drivers for over 20 years for over a hand full of companies."

Your dishonesty is despicable.

[andrew levy]

Hi,

Thanks for the advice, but I am using this driver with an active crossover in order to avoid any components such as capacitors and chokes in the way. Therefore I would not like to add a capacitor, especially not in series.

Regards,

Andrew

[andrew levy]

I guess in your opinion Isobarik is not a good thing for Hi-Fi. Would you care to elaborate as to what problems they yield.

As far as a good 12 inch woofer, what choice do you think would be better than the Dynaudio. I have tried a few, and I have liked this one best, the box is huge though which is a pain.

Regards,

Andrew

[AJinFLA]

--

[AJinFLA]

You have an active crossover with no capacitors "in the way"?
Is the pathway from the source media to XO low pass capacitor/choke free as well?

cheers,

AJ

[AJinFLA]

>
>
> A capacitor in series, will ruin any woofer. I would not go
>that way.
>
>

Does logic dictate this?

cheers,

AJ

[spock]

Andrew, The air space between the two drivers cushions the coupling of the two drivers. The air acts more like a rubberband rather then an inert material. I have made a few designs using isobarik type setup, and none sounded good enough to keep or market.

I have the older KEF 104/2 system and it just doesnt sound right either.
The older totem model used this setup, and then bass just wasnt right there either.

All the isobarik does is double the mass and the BL of the driver, only not in the proper way as the air cushion doesnt completely couple the drivers.

The reason dynaudio woofers are not very good for a subwoofer design.
* PP cone, rather soft and will warp at lower frequencies
* Short excursion capability compared to most woofers.
* High Q which will need a large box
* Low BL, suggesting sluggish performance. This woofers motor has the force of most 6” drivers.

The only thing these woofer have going for them is the large voice coil diameter.

For the $$ you can get for these drivers on ebay, there are many good choices out there. I think the Aurasound 10" is a very good choice for the $$ (12" is ok also) as it uses underhung voice coil to keep distortion levels low and a stiff aluminum cone.

The motor force is double of the Dyns, excursion capability is also double. Much more linear then the dynaudio, thanks to the underhung voice coil design.

The peerless subs are also nice, more brut then the aurasound, but not as linear.

Ive worked on some aurasound designs, so naturally, I like these, but there are many good choices out there. “Vasyachkin” seems to have tried many subs, if you want a second opinion.

[andrew levy]

Althogh I must say they sound pretty good!! So I will hear suggestions for others such as the Auras (I don't know if these are for sealed or vented enclosures). However I am looking for a sealed enclosure. For Hi-Fi use, not subwoofers, not home theater. Anyone else with suggestions??

Regards,

Andrew

[andrew levy]

AJ,

Let me guess, your current setup has a capacitor in series with the woofer?? Hey that's fine, different stroke for different folks!

Regards,

Andrew

[andrew levy]

What suggestions do you make, for a sealed enclosure, strictly Hi-Fi use 6db per octave crossed over at 250Hz??

Thanks in advance,

Andrew

[vasyachkin]

how about model NS15-992 from here:

http://www.madisound.com/pdf/printcatalog/aurasound.pdf

i can see only two downsides to this driver - low efficiency and high cost but if you're going active might as well.

i know its called a subwoofer but it also says in the specs that its good up to 1.5 khz ... so its really more like a SUPERwoofer than a SUBwoofer. i think it matches your application (30hz - 250hz sealed) perfectly. with an aluminum cone and underhung motor it should be very clean in that range.

[vasyachkin]

no i actually haven't tried a lot of subs ...

but i do have the best one :)

and i did a lot of research/thinking before buying it ...

i don't think that Aura is good for the money ... but when money is no object i think it would be THE woofer to get. underhung motor can never be a good value (becaue its expensive to make) but slowly more and more high end manufacturers are turning to this scheme because it is more "audiophile" so to speak. recently Accuton turned to underhung neodymium motors and now scan-speak also did with the illuminator. but Aura did this long before them.

i did not get the Aura myself because i got this:

http://www.audiopulse.com/products/subwoofer-drivers/lms-ultra

but i got the LMS to work below 80 hz. for use up to 250hz i would have gotten the Aura.

[vasyachkin]

there are many good woofers out there ...

it depends on how much performance you need, how big of a box you're willing to have and how much money you're willing to spend

if you're looking for a driver to work below 250hz then bigger will generally be better but also cost more and require bigger box so you have to figure out your priorities there

[AJinFLA]

>AJ,
>
>Let me guess, your current setup has a capacitor in series
>with the woofer??

No. My dipole woofers are actively equalized to target Q. My DIY subs are servo driven. Neither require or would benefit from the method suggested to you by Daryl for your particular application.
He gave you good advice even though you do not understand it. It is not the only solution, but your reason for rejecting it was illogical. There are plenty capacitors, resistors and inductors in the signal path of *your* stereos electrical signal before the soundwave is emitted by the woofer.

>Hey that's fine, different stroke for different folks!

Indeed. But not different physics.

cheers,

AJ

[spock]

Vasy, the aura is not expensive at all. I was refering to the 513 model which is $149.
Which is just about as good as the very expensive model. The difference between the two is very small....a little more excurion and power handling for the expensive model.....everything else is about the same.

[andrew levy]

AJ,

How are you crossing over your dipole woofers to your mids or tweeters??

I am not knocking Daryls advice, it's just that in my case for other reasons, it defeats the purpose of what I am trying to do.

I don't disagree with you that it's pretty difficult to build a stereo system without capacitors, inductors and resistors. That does not take away from the fact that some consider that a woofer being driven directly by the output of an amplifier might work better than one being driven by an amp with a capacitor in series.

What physics are you talking about, what law of physics claims that a capacitor does not alter the perfomance of a driver, or that it improves it??

Regards,

Andrew

[Rudy Jakubin]

What physics are you talking about, what law of physics claims that a capacitor does not alter the performance of a driver, or that it improves it??

Regards,

Andrew


The box is analogous to an electrical circuit.
i. e. capacitor, resistor and inductance...

[vasyachkin]

but $150 is not exactly cheap ... so its actually in the area where its not cheap any more and not state of the art yet

the more expensive driver is no longer in the range where price is even a consideration so ironically i think its actually a better value

LOL

[andrew levy]

for the great information, I will do my research and determine the next step.

Andrew

[vasyachkin]

i guess we are asking the wrong questions

perhaps the question should be - will adding a capacitor make the amplifier work harder to drive the speaker to the same level of output ?

i don't know ... but i doubt that it will make it easier.

i would rather put a resistive vent in the box to damp down the bump in response than to put a capacitor in there. its not that i think capacitor would somehow damage the sound but driving the capacitor itself might be extra (unnecessary) work for the amplifier (although i am not sure if this would be the case in the particular application). of course driving the resistive vent would also be extra work ... on the other hand it would actually flatten impedance instead of making it go crazy ... so i cannot say for sure which solution is better

what about using a parametric EQ and just equalizing the bump ?

to me this would not really be a question as i am already running several parametric equalizers on my woofers but if your system could possibly do away without them (depending on your room acoustics) i don't know if adding one just for this one purpose would be worth it ...