Can someone explain the theory behind "sound reinforcement drivers"?

[Stephen D]

Also

Another thing I wanted to mention or ponder before but forgot.

Dual chamber reflex cabs could be a help to alleviate the worries
of over excursion in the upper bass from using a low port tuning
because it gives 2 port tunings (Typically an octave apart), spreading the active port support bandwidth over a wider range. I built one of these about 10 years ago that I use for my home HiFi that has a low port tuning near 30 Hz & upper port tuning near 60 Hz.

Still though, back on track with the focus of the post that started this thread, the vast majority of high efficiency sound reinforcement drivers don't have T/S specs that lend themselves
well to sub 40 Hz port tunings, at least not without a considerable
shelving dip in bass efficiency.

 

[kelticwizard]

...not everyone owns a table saw, etc. but out in the real world T-S is only half, if that, of what you need to get flat response.
Beg, borrow, or steal some test equipment.
Then be prepared to cry real tears.

Grey

Grey:

I did, some time ago.

I found that the Thiele-Small numbers held up pretty well with the following provision. I found that the predicted half space, (2 pi), response for bass-that is the response predicted when the speaker was on the floor with no walls around it-happened when the speaker was put at the junction of a floor and a wall.

I realize that the floor and the wall junction actually made it quarter space, (1 pi), response, but there you go.

When I measured the speaker outside, with no walls around it at all, just the ground, the bass rolled off incredibly high. Put it on the floor inside, against a wall, and measured much closer than any additional walls, (thereby minimizing their reflections), and I got something reasonably close to the predicted half space response for bass.

I didn't make a big deal out this because in any uses that I would use speakers, they would be on the floor and near a wall.

Am I the only one who noticed this?

 

[Cal Weldon]

Thanks for the answers

I appreciate the input from all you respondants. The reason makes so much sense, that it's little embarrassing having asked.

Thanks also to Stephen D who in post#21 recognized the fact we had strayed a bit from the topic. Oh well, it gives the speaker junkies a chance to shoot up, if you will.

Cheers
Cal

 

[GRollins]

Wizard,
Something I should put in is that midranges typically have more predictable response, though still not as good as I'd like. It's that below-100 Hz stuff that makes me crazy.
Regarding PIs...my typical usage is half space. I've got a floor, but do my best to minimize wall reflections, as they're hell on imaging. Granted, you can't do much to damp a 30Hz wave, but I space the subs 1/3 of the way down the room and at thirds from the side walls--at least that tends to reduce standing waves. Given that my sub towers are 7 feet tall (six 12" Titanics per side), they approach a line source configuration. Still, they roll off badly without help from the crossover (measured in-room). Currently, I've got them +-3 dB from 20Hz up to the crossover point at 70Hz. I'm not satisfied yet. My goal is still to servo the beggars with individual amps. My limiting factor, as always, is time.
There's no question that I could get more bass against a wall, in a corner, etc., but at the cost of much more uneven response.

Grey

 

[mrfeedback]

Eric,
Yeah, I vote for the groin effect.

Grey

I discussed this with my sister and her reply was that this is stimulating the 'Root Chakra'.
Aussies will understand the humour in this.

Eric.

 

[Centauri]

Cal,

Another point which has not been mentioned, as that a lot of Pro Sound work would involve horn loading. Due to the reduction in driver Fs due to the horn load, a 45Hz driver matches up pretty well with a 30Hz sub horn for some serious low end.

Cheers

 

[fizzard]

Cal,

Another point which has not been mentioned, as that a lot of Pro Sound work would involve horn loading. Due to the reduction in driver Fs due to the horn load, a 45Hz driver matches up pretty well with a 30Hz sub horn for some serious low end.

Cheers

Yeah I agree. It also depends somewhat on the type of "pro." For PA/DJ use you get a lot of sealed and some bass reflex. For touring it's pretty much horns all the way. You can get away with 1/4 of the amplification.

 

[phase_accurate]

You can get away with 1/4 of the amplification.

....... and three times as much truckload ........

Regards

Charles

 

[Brett]

Unfortunately thats also what guitar-players, drummers, soundmen etc prefer our instruments to sound like !

One of my next experiments will be two ELF subs (using RCF L18P300 drivers).
And yes, I prefer the sound of an uncompressed bass over the mainstream bass-sound even if it doesn't get as "loud" using an 1 kW amp as some 200 Watt instrument amps go.

Regards

Charles

Did you ever do these experiments and if so what were the results. I have an L18P300 and it models well in 100L ported to 40Hz and sealed in the same vol gives a 72hz q=0.6 which would be useful for many gigs.

I'll xover to a 10 + 1"/horn above 300Hz.

 

[phase_accurate]

Hi Brett

No I didn't have time for this so far. They are still sitting in their original package waiting to be abused.
I also wanted to use a box around 100 Liters. As a closed box it could probably compete with many of those ubiquitous 4x10" even without equalising.

Regards

Charles

 

[fizzard]

....... and three times as much truckload ........

Regards

Charles

Yeah I've always wondered that myself, but it's not entirely true. Horns might give you fewer drivers per ft^3 of space, but in terms of SPL per ft^3 of space you probably come out smaller with horns.

I've heard a bass horn with 2 18" JBL drivers dominate 4 2x18" sealed Yorkville enclosures. The horn was marginally larger than the four Yorkville enclosures.

My goal is still to servo the beggars with individual amps.

I thought you were against feedback