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Old 17th March 2011, 03:07 AM   #681
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Quote:
Originally Posted by jbell View Post
Art:
I'm not sure what you recall for the phase swing for the ss15 in the 200-250 range.
Yes, that is what I recalled, a large shift with about 190 Hz as the turnaround.
200-250 Hz would be a poor choice for a crossover point if phase response around the crossover region is regarded as important.

Have you recorded Magnitude or Phase responses of the SS15 using Smaart, or have you just been using it's RTA functions?

Art
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Old 17th March 2011, 03:38 AM   #682
Djim is offline Djim  Netherlands
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JBell, I have a suggestion I think you should consider. Fist of all, you never are going to really boost the 40Hz if you don’t give up somewhere down the line.

My suggestion is simple but needs explanation. First of all, your SS15 as it is now has serious trouble to load below it 1/3 wavelength of 47Hz. Also you have to set your Low-cut filter at 38Hz for full power. This means it starts to cut around 44Hz. So even if it is possible to gain in the low end it will be cut anyway.

Now, so my first suggestion is to drop its fundamental. Then you can set your filter to 32Hz and it starts to cut around 38Hz. This is 6Hz lower and means 3dB less cut at 40Hz…

Secondly if you redesign the SS15 basic fundamental and make sure its 1/3 wavelength is at 42Hz (this is possible I think) the cab will do 21/2 dB better at 40Hz. This at cost of 11/2 to 2dB overall (accept below 50Hz!). But remember you have 3dB boost at 40Hz!

So the difference in reality at 40Hz is +/- 5dB!!!

Also if you force a cab below it's 1/3 wavelenght point you will increase it's saturation level (power compression). So if you start to boost at 40Hz in a try 'to make' up you will loose gain in maximum power. So maybe your SS15 now has more SPL in full load it will be less efficient.

But there is more to the story. Because you can drop its fundamental, the highest excursion also drops. This means you make up the loss in the higher region with EQ just there where the excursion is minimum!

Look at the 4 cab situation. You will see the suggested cab reaches 40Hz at ZERO dB loss! The suggested cab has a rise at 45Hz so compression loss under high load is kind of equalised. This means almost no EQ in the low, but instead higher up and you have what you asked for; serious bottom end from the SS15!

I'll show you the difference between your SS15 and my suggestion. Remember this example doesn't show the low cut filters or compression levels so the difference is bigger at 40Hz in reality...

What do you think?
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Last edited by Djim; 17th March 2011 at 03:59 AM.
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Old 17th March 2011, 04:36 AM   #683
jbell is offline jbell  United States
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DJIM:
I'll have to check my filters, but I know I use butterworth 48db/oct high pass and LR 24db/oct lowpass. (have to fire up bandmanager tomorrow to check.) I know crown gives a pretty good visual representation of what the filters actually cut.

I've driven myself crazy on this one, and I keep coming back to thinking the SS15 needs to be left alone, it is what it is... It's a great rock and roll sub, but it's not a D&B sub. For that, you are right, you need a much longer path, and the current fold of the ss15 doesn't lend itself to that. I think I'd have to change to something that looks like the attached. Maybe I should try for a SS15DB that can hit those low notes in a single sheet design, while giving up a couple db in efficiency???
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Old 17th March 2011, 05:03 AM   #684
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by jbell View Post
DJIM:
I'll have to check my filters, but I know I use butterworth 48db/oct high pass and LR 24db/oct lowpass. (have to fire up bandmanager tomorrow to check.) I know crown gives a pretty good visual representation of what the filters actually cut.

I've driven myself crazy on this one, and I keep coming back to thinking the SS15 needs to be left alone, it is what it is... It's a great rock and roll sub, but it's not a D&B sub. For that, you are right, you need a much longer path, and the current fold of the ss15 doesn't lend itself to that. I think I'd have to change to something that looks like the attached. Maybe I should try for a SS15DB that can hit those low notes in a single sheet design, while giving up a couple db in efficiency???
I think it is possible within the concept. And in the end the total SPL wont be that different. And the more cabs the smaller the difference (except for the low end).

Now I think you'll need about +7dB or +8dB at 40 to make it up. But because of the filter and the higher 1/3 wavelenght (47Hz) + higher roll off below 47Hz you loose quiet a lot around 40Hz (altough the filter isn't counting in power loss). Btw the extension of the horn path needs an extra 30cm (11.8inch) to get 1/3 WL to 42Hz. With using the non-used space, lowering the mouth (that's where you loose dB's) and careful thinking this might be possible...

And don't forget the harder you drive, the better a lower tuned SS15 will perform (if designed correct).

For your concept you just showed, be careful there, you start with two 90 degree corners that are facing. We are still working on bettering the THAM since Oktober last year just to repair the 'dip damage' that didn't show up in HornResp...

Last edited by Djim; 17th March 2011 at 05:13 AM.
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Old 17th March 2011, 02:48 PM   #685
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Can the ss15 be crossed at 250hz?

Quote:
Originally Posted by weltersys View Post
I see two possible problems with crossing a SS15, (or any TH with a FB 50 Hz or lower) at 200 to 250 Hz .

The TH may be a lot tighter pattern than the midbass above it at 250 Hz, systems always sound better when dispersion patterns match at the crossover point.
My Keystone TH is about 90 degree dispersion at 125Hz (6dB down point), it probably is only 45 degrees at 250. I'd expect the SS15 may even be more narrow that high, considering the mouth shape differences between the two cabinets.
It would take a huge,very long mid horn to have 45 degree pattern control at 250 Hz.

Problem two may be a difficulty in matching phase at the high crossover point, IIRC the SS15 phase is going through a big phase swing that high. Matching the phase (using delay) at 250 Hz will result in a rapid phase change below the crossover point, which sounds unnatural.

Jim, have you ever posted the phase response of the SS15 ?

Does it match the simulation ?

Art
Thank you, very thorough answer.
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Old 17th March 2011, 04:30 PM   #686
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So cross it at 30-150Hz?
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Old 17th March 2011, 05:07 PM   #687
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Quote:
Originally Posted by 4pyros View Post
So cross it at 30-150Hz?
More like 38 or 40 to whatever. 30 Hz won't give the SS15 4015LF the excursion protection needed for high power use.

150 is high enough that some of the vocal range will be heard through the subs, so unless the subs and highs are both lifted on to scaffold, the frequency response will be affected by people in front of the cabinets.

If you are going to leave subs on the ground, 125 Hz is kind of the upper range I would go with. Since a fireworks audience is more spread out than a rock audience, you could probably get by with a 150 Hz acoustical crossover.

Without seeing the actual phase and magnitude response of both the sub and top cabinet driven with the same voltage, it is hard to suggest what points would work best.

It is highly unlikely that a symmetrical crossover will give the best results, for example you may find 110 Hz BW for the sub with 120 LR for the top works best after the proper delay has been applied.

Proper crossover implementation makes as much difference in sound as driver or cabinet selection, to do them right is not an easy task, though with DSP (digital signal processing) it is about 10 times easier than trying to do a good crossover passively.

Of course, with the path length in a TH, it is impossible to properly align the top to the bottom without delay unless putting the tops about 8 feet behind the subs is an option.

Art

Last edited by weltersys; 17th March 2011 at 05:12 PM. Reason: # error
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Old 17th March 2011, 06:56 PM   #688
tb46 is offline tb46  United States
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Hi jbell,

Looking at your sketch in Post #683, I've done that one, and others, and it does not get you there within the 24"x30"x22" outside dimensions of the SS15. I'm very close to being convinced that you maxed that one out.

The other thing that I realized after just a few stumbles is, that you have to actually draw the path, and add some real dimensions, or you can talk yourself into all kinds of great solutions that will not work when you try to lay it out in wood.

Regards,
__________________
Oliver
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Old 17th March 2011, 08:32 PM   #689
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Quote:
More like 38 or 40 to whatever. 30 Hz won't give the SS15 4015LF the excursion protection needed for high power use.

150 is high enough that some of the vocal range will be heard through the subs, so unless the subs and highs are both lifted on to scaffold, the frequency response will be affected by people in front of the cabinets.

If you are going to leave subs on the ground, 125 Hz is kind of the upper range I would go with. Since a fireworks audience is more spread out than a rock audience, you could probably get by with a 150 Hz acoustical crossover.

Without seeing the actual phase and magnitude response of both the sub and top cabinet driven with the same voltage, it is hard to suggest what points would work best.

It is highly unlikely that a symmetrical crossover will give the best results, for example you may find 110 Hz BW for the sub with 120 LR for the top works best after the proper delay has been applied.

Proper crossover implementation makes as much difference in sound as driver or cabinet selection, to do them right is not an easy task, though with DSP (digital signal processing) it is about 10 times easier than trying to do a good crossover passively.

Of course, with the path length in a TH, it is impossible to properly align the top to the bottom without delay unless putting the tops about 8 feet behind the subs is an option.
Art; Thanks for all that detal!
I was looking at 150 For the high end, my 15" mids in the ported box start to peter out below that.

You are saying that if I stack all my speakers on top of each other. I will have to delay the tapped horns by the path length in the box? Wouldn't it work off the other side of the speaker at the mouth?
Andy
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Old 17th March 2011, 08:34 PM   #690
jbell is offline jbell  United States
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I think art is confusing front loaded horns with tapped horns.

The ss15 driver is in the mouth -- no delay needed if tops are above subs.
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