I am in the process of layout/design of my new theater room. I am going to be using PI 4 Speakers for LCR, and PI 1 Speakers for Surrounds. I designed a set of OD Horn Speakers to compliment the LCR and surround speakers as flanking subs to tame room modes. So the frequency range is 50-200hz
Since this is my 1st attempt at Hornresp and Sketchup, I am looking for input on my design and folding before proceeding further. So there will be 7 total of these flanking subs the front 3 will be under the PI 4's and the 4rears will be under the surrounds in a column configuration. The will be driven with 20 watts RMS.
I will be using a miniDSP 10x10hd, and the plan is to cross the flanking subs, with there respective mains, as well as matrix the LFE channel to theses subs as well for frequencies above 50hz, and then use the Low LFE subs for everything under 50-60hz.
One thing you find in working in real rooms versus sim land is that a flat response in sim land will be greatly overblown in the real world. I have found that you can tailor the response of a sub to behave with a flat response in a real room.
The method used is to incorporate a bit of a falling response.
Advise taken, I am using 1/2 space sim in hornresp, so I assumed that would be close to in room...?
Yes and no.
Most reasonably sized rooms will have a bit of reflection reinforcement i the nether regions.
It really starts to get useful below thirty hertz. You get about 3 db here, and usually about 6 to 8 at 20 hertz.
Below this you are really working in the pressure field, as in the room is much to small to create a reflected true to length wave of the sounds. So you get even more reinforcement. At 16 hertz a great many studies have shown that there is about ten plus db of room gain.
Now for the good/bad news. Not very much program material has large peaks down that low. It's mostly higher harmonics or multiples of the low frequency fundamental notes.
Even nasty pipe organs are not that killer down low. A few are, and I have the recordings to show them off.
Some movies to have the odd bit of thunder.
SO what does this have to do with your box design?
You can reduce the size but not the path length and create a design that will produce what you want in room.
If you are really keen on getting this right there is a fairly simple method you can use if you have a measurement microphone and REW.
Don't worry a whole bunch over the group delay effects. ( sorry chrapladm )
I have done quite a few horn loaded subs that should have had built in echo according to the naysayers. But the effects are very difficult to hear in the low end. Horns done well have vanishingly low distortion. In fact I have yet to have heard one that I found to be problematic in any way.
My background is in music by the way, I played in the brass section, and still can tune by ear an instrument I have not regularly picked up in 26 years. And I'm very picky in terms of quality of bass reproduction. I have heard most everything live and remember exactly what it sounds like. It's what drove me to start designing speakers in the first place!
Last bit of advice. Your ULF sub would be better as a FLH (front loaded horn) I can always tell the sound of a tapped horn. I never really enjoy them.
They tend to sound like vented boxes. A bit whooly on the low end. If you like that then it is you ticket to happy ville.
Last bit of advice. And this is a pat on the back at the same time.
Trust Hornresp if the following conditions have been met:
You have tested your drivers and are using the measured parameters as input to Hornresp.
You build exactly what you sim ( your folds look great )
Brace brace and brace some more. Horns are high pressure devices and the highest pressures are closest to the cones.
So you should stick with your first design of the mid bass horns. A falling response will not help you in this range as there is very little room gain at the frequencies the midbass horn will be operating at.
Way to large of a rear chamber on the idea for the riser. You have basically designed a box with a very long vent.
Never load two horns into a single mouth the same size as it would be for one horn.
If you want a common mout you can do this. But it should be the summed area of two individual horns.