Open Baffle: long-term S.Q., what's your experience?

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T

Telstar

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Joined 2007
marec said:
Sorry, I think I misunderstood. If you are not starting from an existing production sub, but want to use a high QTS driver in an open baffle, please use MJKs designs. They will save you so much experimentation. Having established a baseline, then you can go on to perfection...

Use lowthers offset in a 48x 20 baffle, put two cheap 15As each side, use a cheap ultradrive x-over and find the music....

Rgds
Click to expand...

I have room limitations that do NOT allow me to use side drivers nor a baffle wider than 40cm.

I do not see much problem in the bass part, since I have studied other projects (including MJK) ones, and I'll equalize the bass with the active sub and if more if needed digitally.
 
M

marec

Member
Joined 2006
I must admit, a major part of the OB experience for me is in the Bass...
If you use some sealed/vented source of bass, you may miss something!

Whoops! missed something again! When I say 2x15As per side, these are in the same plane as the wideband driver...
So, a 48x20 baffle has 2x 15" drivers on the vertical axis and the 8" driver offset above.

Again, see MJK's excellent articles.
Rgds
 
M

marec

Member
Joined 2006
Telstar said:
I will be using OB baffle, with U frame to compensate for a narrow baffle. They'll be powered and filtered by a plate amp. Clear now?

As I said I will use as base MJK projects and others that work.

The problem is to find a widerange to pair. See the thread i made on this purpose:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1774009#post1774009
Click to expand...

Yes, OK. But, you're still going to have to either:
(1) Try the different xover frequencies / slopes for the plate amp and a chosen OB(size) wideranger.
or
(2) simulate them.


I really recomend simulation...

Rgds
 
T

Telstar

Member
Joined 2007
marec said:


Yes, OK. But, you're still going to have to either:
(1) Try the different xover frequencies / slopes for the plate amp and a chosen OB(size) wideranger.
or
(2) simulate them.


I really recomend simulation...

Rgds
Click to expand...

Yes, you are right of course. I'll do simulations first and then finetuning of the crossover freq. Once i build the baffle, i'll have little margin, as it has to be waf-approved (i.e. nice veneer, cannot really play with mdf)
 
T

ttan98

Member
Joined 2006
marec said:


Yes, OK. But, you're still going to have to either:
(1) Try the different xover frequencies / slopes for the plate amp and a chosen OB(size) wideranger.
or
(2) simulate them.


I really recomend simulation...

Rgds
Click to expand...

I have MJK stimulator s/w as well, however I find using an active x-over eg., DCX2496 is far easier, you can dial the frequency you need easily and more importantly quickly. Adjust the freq until you find the response flat, assuming you can measure the FR curve.

The DCX 2496 is not expensive, about US$250, when you are happy with the sound and configuration, then one can design the passive x-over for it. Selling the DCX is very easy and many people are looking for 2nd DCX, and 2nd DCX holds up its value very well.

DIY speakers hobby is cheaper than buying expensive speakers nowadays. It has a further advantage of being able to adjust the sound to ones taste, room conditions, etc.

Cheers.
 
M

marec

Member
Joined 2006
I've sung the praises of the ultradrive until I'm sick in the head! At low frequencies, playing with passive x-overs costs a fortune! The purchase of an ultradrive can save this.
Incidentally. the same is true of an ultracurve! Find what your room does to the signal, a couple of OP-amps and there you are...

Rgds
 
T

ttan98

Member
Joined 2006
marec said:
I've sung the praises of the ultradrive until I'm sick in the head! At low frequencies, playing with passive x-overs costs a fortune! The purchase of an ultradrive can save this.
Incidentally. the same is true of an ultracurve! Find what your room does to the signal, a couple of OP-amps and there you are...

Rgds
Click to expand...


Some audiophiles don't like the sound of standard DCX, I think Ultradrive which may sound better, and more expensive too. For the diehards they prefer passive x-over whatsoever.
Passive x-over are expensive if one incorrect design the x-overs there you are left with many expensive caps and inductors on the shelf which amount to many hundreds of dollars or pounds, and difficult to sell as well.
 
D

dzzmiller

Member
Joined 2008
ttan98 said:



Some audiophiles don't like the sound of standard DCX, I think Ultradrive which may sound better, and more expensive too. For the diehards they prefer passive x-over whatsoever.
Passive x-over are expensive if one incorrect design the x-overs there you are left with many expensive caps and inductors on the shelf which amount to many hundreds of dollars or pounds, and difficult to sell as well.
Click to expand...

I think the two channel out DEQ sounds better than the 6 out DCX. But the DEQ isn't a crossover.

One specific problem of the DCX is accurately processing 24/96.
 
ashok

ashok

Member
Joined 2002
Any idea if the peerless XXLS 12" will replace the alpha 15A
Click to expand...

No! They have completely different Qts. The XXLS is about 0.45 and the Alpha15A is 1.26 .
The XXLS you mentioned is still useable I guess but you will need a lot of bass equalisation . I think the Alpha15A can get by without any as you can see from some earlier posts in OB threads. Both drivers also have different sensitivity.
The XXLS most likely cannot be good up to 800Hz . They have a severe dip at about 500Hz and a 15 db climb to just under 2 Khz!
The Alpha15A should be quite useful till 800 Hz. but even that has a steep climb after 1.5Khz.
Maybe the XXLS will work better as a Ripole ? You will need to roll off early to avoid problems with the peak at about 2Khz. Roll off at not more than 300 Hz I would guess.

Cheers.
 
gainphile

gainphile

Member
Joined 2007
gainphile.blogspot.com
Re: Re: Re: Open Baffle: long-term S.Q., what's your experience?

KT said:


Wow, thanks guys for all the input.

I guess the quirk I'm thinking of isn't necessarily a frequency response issue, but just that the bass on a pure OB is often described as loose and kind of soft. I suppose that this is one of the trade-offs for getting such a natural midrange response; being rid of the box and all.
Click to expand...

OB bass in fact has more tightness and resolution. What they lack is 'slam'. Actually 'lack' is incorrect word, more precise is 'different'. Hear the contrabass / cannon on a proper OB system and it will be difficult to get back to boxed bass.

http://www.youtube.com/watch?v=x61YMdowJbQ
 
T

Telstar

Member
Joined 2007
ttan98 said:
I have MJK stimulator s/w as well
Click to expand...

I dont, but I'll send an email to Martin shortly and see if I can buy it.
I need to run LOTS of simulations asap, I have too many ideas that need a reality check :)

however I find using an active x-over eg., DCX2496 is far easier, you can dial the frequency you need easily and more importantly quickly. Adjust the freq until you find the response flat, assuming you can measure the FR curve.

The DCX 2496 is not expensive, about US$250, when you are happy with the sound and configuration, then one can design the passive x-over for it.
Click to expand...

It's not a matter of money, but of signal purity. As a design tool it can be useful... if you are then going to design a passive XO later. But I'm not.
I'll use the plate amps XO and volume, with room measurements (of course) and that's it.

DIY speakers hobby is cheaper than buying expensive speakers nowadays. It has a further advantage of being able to adjust the sound to ones taste, room conditions, etc.
Click to expand...

I totally agree with this statement.
 
Scottmoose

Scottmoose

Member
Joined 2005
wodendesign.com
Just be careful with this 'signal purity' business. It can often cause more problems than it solves.

For e.g., take the case of an OB, where you have a wide-band driver, and a bass unit. You run the wide-band driver completely filterless, and the LF unit active, perhaps using the XO built into many plate-amps to low-pass the bass driver so you're not entering into its breakup modes. That's OK for the LF driver (to an extent), but running the FR driver sans filters on a baffle is not necessarily a good idea. The bass driver nominally takes some of the weight off its shoulders, but, especially as SPLs increase, you still haven't done anything to control the wide-range units' excursion (given that it too is still trying to reproduce the LF), so amplitude modulation distortion / phase modulation distortion are going to rocket. Is the 'purity' of not high-passing it worth that? YMMV as always of course, but personally, I'd say no chance.
 
T

Telstar

Member
Joined 2007
Scottmoose said:
Just be careful with this 'signal purity' business. It can often cause more problems than it solves.

For e.g., take the case of an OB, where you have a wide-band driver, and a bass unit. You run the wide-band driver completely filterless, and the LF unit active, perhaps using the XO built into many plate-amps to low-pass the bass driver so you're not entering into its breakup modes. That's OK for the LF driver (to an extent), but running the FR driver sans filters on a baffle is not necessarily a good idea. The bass driver nominally takes some of the weight off its shoulders, but, especially as SPLs increase, you still haven't done anything to control the wide-range units' excursion (given that it too is still trying to reproduce the LF), so amplitude modulation distortion / phase modulation distortion are going to rocket. Is the 'purity' of not high-passing it worth that? YMMV as always of course, but personally, I'd say no chance.
Click to expand...

Thank you for the informative post. You got precisely my thoughts and explained the possible issues.

This makes choosing (and matching) the FR driver very critical. IIRC, high sensitivity and impedance and sufficiently big size are the requirements to pay most attention. Am I being correct?
The Goodmans 201 works, for instance. I'm in the process of driver shortlisting. Besides the above, which both rolls off a bit too soon and its basically unavailable, the ones that look the best (and dont cost an arm and a leg are:

12-inchers:
Audio Nirvana Super 12 Cast Frame

10-inchers:
Hemp FR8/FR8C
Audio Nirvana Super 10 Cast Frame
Beyma 10AG/N (very cheap, could be bought only to try)
Alpair 10 fullrange
 
T

Telstar

Member
Joined 2007
ashok said:


No! They have completely different Qts. The XXLS is about 0.45 and the Alpha15A is 1.26 .
The XXLS you mentioned is still useable I guess but you will need a lot of bass equalisation . I think the Alpha15A can get by without any as you can see from some earlier posts in OB threads. Both drivers also have different sensitivity.
Click to expand...

Would the Peerless SLS-315 or Alpha 12 or Beta 12 work 30-200hz in U frame (without much EQ, just bass boost at lets say 20hz and highpass)?
 
D

dzzmiller

Member
Joined 2008
ashok said:


No! They have completely different Qts. The XXLS is about 0.45 and the Alpha15A is 1.26 .
The XXLS you mentioned is still useable I guess but you will need a lot of bass equalisation . I think the Alpha15A can get by without any as you can see from some earlier posts in OB threads. Both drivers also have different sensitivity.
The XXLS most likely cannot be good up to 800Hz . They have a severe dip at about 500Hz and a 15 db climb to just under 2 Khz!
The Alpha15A should be quite useful till 800 Hz. but even that has a steep climb after 1.5Khz.
Maybe the XXLS will work better as a Ripole ? You will need to roll off early to avoid problems with the peak at about 2Khz. Roll off at not more than 300 Hz I would guess.

Cheers.
Click to expand...

The aluminum XXLS has a higher usable frequency, but I still won't work crossed at 800. I do think there's merit in looking at hifi, not pro, woofers. Especially if doing the bi-amp active xover thing. There are a few that have low Fs and spl ~95 that can be crossed at 800-1000. These are all going to be low Qts.
 
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