Dispersion hi-mids with horizontal 2x10(s)

[Hippytone]

I hope you'll forgive me dragging this one up again, but I have a specific question regarding the frequency at which this comb effect thingy starts to become an issue.
I'm using a GK 2x10 combo with an additional 2x10 cab underneath. I have done a couple of gigs using the combo & cab on their sides to get a single vertical column of 10's and this does seem to cause the 1001RB head in the combo to get rather warm due to the altered ventilation characteristics due to it being on it's side.

The sound I'm going for is a typical Motown P-bass thump with flats & foam mute. Tone is rolled pretty much off.
So lots of low mids and no real top end as the amp treble control is rolled off completely and high mids flat.

Can anybody tell me whether I might escape the dreaded "4x10 cancellation phenomenon" given these settings?

I've had a pretty good read of most of the threads on here regarding this, and now I'm hoping that some savvy person like Alex or Bill might jump in and name some frequencies.

Thanks
Nick

[Bill Fitzmaurice]

Put the 2x10 extension vertical atop the combo. The difference between the dispersion of two vertical versus two horizontal drivers is a simple equation, it's doubled.

[Hippytone]

Thanks for that Bill.

[Phil Starr]

Bill is right about the dispersion and the best practical solution.

I'm going to suggest something to think about. Old 8x10's were technically a bit of a dead end, They solved a lot of the technical problems at the time. Power handling, reliability, plenty of efficiency all sorted but were highly coloured, too small a box for that many speakers and comb filtering problems. However because something has technical limitations it doesn't mean it is bad. It may be that the comb filtering with it's off axis rolling off of the top end is just the old school sound you are looking for.

If your sound is just as you like it and you can pick yourself out of the mix then I wouldn't go in for speaker balancing. Get a long lead and go out into the audience area to see how you sound. If you are struggling to hear yourself on stage then Bill's advice is the best way to go.

[Hippytone]

Thanks Phil, absolutely agree regarding the value of "dead ends"... While four legs is good, two legs is not ALWAYS bad !

I very rarely have a problem with hearing myself on-stage... The issue is more centred around those gigs where there's no PA support for bass, where I would like the audience to hear something vaguely similiar to what I'm hearing

It's one thing to bathe in lovely lo-mid, old school thumpiness on stage, it's quite another to suspect that you may well be filling the room with weird blobs of infra-sound, which are only going to find favour among mushrooms & manta-rays!

This was the reason behind the initial question regarding the "real-world" frequency point at which I'm going to start losing equal definition across the room due to comb filtering.

Edited February 24, 2017 by Hippytone

[Bill Fitzmaurice]

[quote name='Hippytone' timestamp='1487943727' post='3244405']
This was the reason behind the initial question regarding the "real-world" frequency point at which I'm going to start losing equal definition across the room due to comb filtering.
[/quote]Comb filtering doesn't reduce dispersion. It causes uneven response across the sound field in the frequencies where the center to center distance of the drivers is more than one wavelength. With two tens that's from about 1kHz.
The main issue with side by side drivers is that horizontal dispersion is inversely proportional to the width of the source, even when they are spaced close enough together to act as one larger source rather than two smaller sources. A pair of tens side by side will have horizontal dispersion similar to a twenty-one inch driver, and will be noticeable down to at least 600Hz.

[Hippytone]

Thanks for that Bill, that's exactly what I meant.

The combo can't have anything on top of it as that would block the fan. So short of building some spacers, the best compromise would probabably be to put the combo with the speakers side by side on top of the vertically aligned ext. cab I guess... sort of T-shape.

[stevie]

Unfortunately, you're not going to escape the 4x10 cancellation phenomemon whatever you do; you can only make the best of what you've got. If you pay a visit to Bass Gear Magazine and look at some of the measurements (issue 10 has a couple), you'll see that cabinets with multiple full-range drivers have a power response that looks like the Swiss Alps. It's partly combing and partly beaming, although beaming is the main culprit, and it starts about 250Hz (you said you wanted a figure). You only get proper mutual coupling up to 1/4 of the centre-to-centre wavelength frequency - above that you should really be crossing over to a smaller driver.

I'm surprised that they work as well as they do - and clearly plenty of bassists love 'em. But they have about as much "throw" as a mouse tossing a caber. It does, of course, depend on the size of the rooms you're playing in.

Edited February 24, 2017 by stevie

[lownote]

I have no idea what you're talking about, but having been in your audience and not being a fun guy or a manta ray I can assure you that you sound fine Nick. Lots of deep chocolate JV with flats.

Edited February 26, 2017 by lownote12

[Hippytone]

Why, that's very kind of you to say so sir...

fwiw I've always found "The BC" to be a strange interdimensional tarpit for bass!!! Normally everything you play there seems to magically mutate into random bursts of hi-energy 100Hz boom, no matter how quietly you play.
Weird.. still, it's tempting to MASSIVELY over-estimate how important this is to the end product, probably I just need to be slightly less precious

[fleabag]

Do 4x6 cabs suffer the same combing / beaming as 4x10 cabs ?

I'm kinda wondering if my MB 604 pair of cabs would be suffering the same

Edited February 26, 2017 by fleabag

[Bill Fitzmaurice]

The physics are the same with any driver size. Vertically arrayed good, horizontally arrayed bad, at least as far as midrange and high frequencies are concerned.

[Lozz196]

Not understanding the science that well Bill - for that read, not at all - is this why when with a horizontally arrayed cab you get a great on-stage sound that`s perfectly balanced between highs and lows, yet when you walk out into the crowd, all you hear is boomy mush?

[fleabag]

Some for oddball reason, i figured that the small 6 " drivers in my cabs would not suffer so badly as 10's side by side

Strange little cabs these Markbass 604's ...they sound like you'd expect 15's to sound like. They have some serious low end. I wonder if eight 6" drivers shift as much air as two 15's ?

[Beer of the Bass]

[quote name='fleabag' timestamp='1488137792' post='3246240']
Some for oddball reason, i figured that the small 6 " drivers in my cabs would not suffer so badly as 10's side by side

[/quote]

While the dispersion is affected by the same phenomenon as applies to any cab, you'd expect the beaming to begin at a higher frequency with horizontally arranged 6" speakers than it would with 10" speakers, since the overall width of the array is narrower.

Edited February 26, 2017 by Beer of the Bass

[fleabag]

Sounds logical !

[Bill Fitzmaurice]

[quote name='Lozz196' timestamp='1488137677' post='3246238']
Not understanding the science that well Bill - for that read, not at all - is this why when with a horizontally arrayed cab you get a great on-stage sound that`s perfectly balanced between highs and lows, yet when you walk out into the crowd, all you hear is boomy mush?
[/quote]The acoustics of the room aren't as evident close to the cab. I always set my tone and volume standing out in the crowd, if it doesn't sound good on stage I live with it. I'm there to sound good to the crowd, not to myself.
[quote]I wonder if eight 6" drivers shift as much air as two 15's ? [/quote]Eight 6.5" have a total of perhaps 1,000 sq cm cone area, two 15" about 1,600 sq cm. 6.5" will likely have less excursion as well, so they're going to be well shy of a 2x15, much closer to a 2x12.

[fleabag]

That also sounds logical ...cheers

[xgsjx]

Here's a wee Q...

In a 4x10, if you were to put a low pass filter on the 2 drivers at one side, say maybe @ 300hz, would that improve the dispersion?
I'm thinking along the lines of what Alex does with his 6x10, though not sure what his filter is set at or if he uses different drivers left & right.

[MoonBassAlpha]

Only 1 side is run full-range, the other side is low-passed, presumably at a frequency below which beaming isn't an issue.

[Bill Fitzmaurice]

[quote name='xgsjx' timestamp='1488205761' post='3246750']
In a 4x10, if you were to put a low pass filter on the 2 drivers at one side
[/quote]It would work very well. 300Hz is lower than you'd need to go, and it would require a high cost inductor. I'd put the filter knee at 800Hz. Use a 12dB/octave filter, 6dB wouldn't be effective enough to be worthwhile.
This is something the manufacturers should have been doing for the last thirty years at least, why they haven't is a head scratcher. It would be an even more useful mod with guitar cabs, but they're all stuck back in 1968.

Edited February 27, 2017 by Bill Fitzmaurice

[Beer of the Bass]

Is sensitivity an issue with this type of design? It seems like with two columns of speakers doing the lows and only one column working above 800Hz, those frequencies might be less loud when listening from in front of the cab. Though I guess there are plenty of speakers with rising sensitivity through the mids that would probably work well.

[Bill Fitzmaurice]

Sensitivity can be compensated for with EQ. The point of four drivers is low frequency capacity. Above 500Hz or so even a single ten can cover a good sized room.

[Beer of the Bass]

[quote name='Bill Fitzmaurice' timestamp='1488213004' post='3246848']
Sensitivity can be compensated for with EQ. The point of four drivers is low frequency capacity. Above 500Hz or so even a single ten can cover a good sized room.
[/quote]

That makes sense. That 500Hz-1K range is usually easy to adjust with EQ without compromising headroom (unlike the low end).