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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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?
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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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'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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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...
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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
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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,
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,
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
Oliver, although this post was meant for JBell, I'm sot sure if you have read my analyses about lowering it's design Fs and 1/3 wavelenght response at cost of overall SPL (except below 50Hz). Yes total efficiency above 50Hz will cost a few dB's but you can gain +5dB at 40Hz. This will make a huge difference in listening experience and provide the extra bottom. Also with four cabs the SPL difference above 50Hz gets smaller and around 40Hz the total gain will even rise from +5dB to +7dB (since compression around 40Hz will be lower than with the SS15 standard).
I have come up with my final drawing (used the best effort in "eye and hand" control to come as close as possible) and HornResp numbers.
I think this is the only way to reach 40Hz decently (and even below) but I need a little help to work it out more precise and to check my findings...
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Just the points where you see SPL is dropping in the THAM and in the SS15 in real measurements.
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Speed of sound (1128 feet per second) /47hz/3=8 feet
1128/40/8 =9.4 feet
Lower cutoff frequencies generally require a longer horn, or a reduced mouth dimension, both reduce SPL level.
Covering the front panel partially would be a good experiment that could be done in a few minutes with a piece of plywood and a few clamps.
Most of the TH output is from the long path length.
Tapped horns need delay if you want to have time alignment with the top cabinet.
Many people confuse phase alignment with time alignment.
A tapped horn (or regular folded horn) crossed over at 100 Hz can phase align with a top without delay if the filters applied and the path length add up to 11.28 feet. It will sound "OK", but is lagging by one cycle from the top cabinet, which makes it seem less loud, as our ears tend to perceive whatever arrives first as louder.
My Keystone TH, longer than the SS15, judging by the Autosm delay finder function used in Smaart, will probably require about 10 to 12 milliseconds delay to align at 100 Hz.
That may be a few milliseconds longer than the DBX Driverack PA I have been using allows :^(.
Jim,
If you ever bother to use the Phase and Magnitude portion of Smaart, you will see that your SS15 output arrives later than a front loaded speaker at the same distance, as can easily be determined by deducting the measurement distance from each from Auto Sm.
You will find that tapped horns, just like any folded horn, need delay for time alignment.
Read my response to Pyros for a bit more explanation.
Note the delay time required below for the same 2 meter distance testing the BR cabinet compared to the Keystone TH, using the same BW 25 and 125 filters. The difference is the path length.
Art
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