Gumtown's DIY 500 watt quad 6.5" bass combo

[gumtown]

Just a pair of output transistors shorted on one side of the supply, but the class A/B amp generates too much heat for my liking,
and the pending class D amp will be more power efficient and run cooler.

The class A/B modules will be re-purposed for another project.

 

[Arjank]

the 1" horn driver as it can go down to 400Hz,

The cut-off frequency of the horn you use is approx 1.2khz, you really need a bigger horn to get down that low.
What driver did you buy?

 

[Downunderwonder]

Fun times but I can't see 4mm xmax 6.5'' drivers moving that much air.

 

[Arjank]

Yeah I chose 39Hz because many commercial built cabs don't really respond too well to a low B or C.

IME a tuning of approx 48hz will give great results for a low B, my own 210 cab is tuned like that.
If I look at the TSP's of those kevlar woofers I would have suggested a cab size of 8 liters per driver and a tuning between 48-52hz.

 

[gumtown]

The cabinet is what it is now,
the internal volume would have reduced a bit since installing the recessed side handles, and the internal volume the horn takes..

So far it the sound I hear has exceeded my expectations,
get need to get this horn tweaked in, run it's own amp and it will be easier to attenuate..

 

[Arjank]

get need to get this horn tweaked in, run it's own amp and it will be easier to attenuate..

It will be easier to attenuate for sure but you will have a hard time to get the cross-over point as low as 400hz. Your new 1" horn driver may be suitable to get down to 400hz but then you'll also need the appropriate horn(size).

 

[beans-on-toast]

Do you have concerns about fitting a horn amp into the combo and keep everything cool enough? Your original horn driver was on the delicate side for this application. There are some nice products out there to choose from. They recommend the lowest crossover point but you may want to approach that conservatively. A lot of things to consider.

 

[gumtown]

No concerns with heat once the class D amp module arrives, it has a smaller footprint too, so there will be plenty of room for the horn amp module.

This is the horn driver and flare, it's (so called) rating 400Hz to 20kHz 80 watts RMS, 1 & 3/8" thread. The cab sounds OK without the horn, so only a little enhancement from the horn is needed, it won't be working much at all.
The fun will be playing with different frequency ranges to see what works best (to my ears).

This is the amp module for the horn, rated at 100 watts but I don't see it needing to go past 40%.
It is very compact, even with a heatsink fitted

 

[beans-on-toast]

Compact to say the least. It looks credit card sized.

 

[Arjank]

This is the horn driver and flare, it's (so called) rating 400Hz to 20kHz 80 watts RMS, 1 & 3/8" thread. The cab sounds OK without the horn, so only a little enhancement from the horn is needed, it won't be working much at all.
The fun will be playing with different frequency ranges to see what works best (to my ears).

The size/dimensions of the horn determine the cut-off frequency, in case of this horn it is approx 1.2khz. Under that frequency the driver gets "unloaded" and distortion rises rapidly.

 

[gumtown]

The size/dimensions of the horn determine the cut-off frequency, in case of this horn it is approx 1.2khz. Under that frequency the driver gets "unloaded" and distortion rises rapidly.

1.2kHz it is,
Thank You for your valued wisdom

 

[Arjank]

1.2kHz it is,
Thank You for your valued wisdom

No thnx, just trying to give some pointers and I don't want you to blow up your new horn driver
Btw. it's best to keep the xover point a bit higher then the cut-off frequency, IMO 1.5khz.

 

[CDweller]

Will the pirate Hello Kitty sound better than the plain pirate? j/k. This is a thrilling thread, in all honesty. Very respectable that you made the choice to build a better mousetrap. Set backs, schmetbacks. Comes with the territory.

 

[agedhorse]

Yes, that horn looks like ~1.2kHz, the general rule if thumb is to keep at least 1/2 octave above the cutoff (depends on the crossover slope, 1st order would be ~1 octave above)

Below the cutoff, the sensitivity falls, the distortion increases, the directivity falls, and the power handling falls. All of this can be significant.

 

[MarkA]

I shall have to learn some practical electronics for the DIYer - this looks like fun, but I can't play at the moment, only watch on TV.

Agedhorse, cool that you take an interest in these threads!

Pirate Hello Kitty should have a sweeter tone and a softer attack, I'd think, but that is conjecture on my part.

 

[beans-on-toast]

Pirate Hello Kitty should have a sweeter tone and a softer attack...

You'd think so.

Having an amp like that would help with meeting girls at gigs. I have a bright red amp that attracts attention because it's different. Not that Gummy's jolly roger amp isn't distinctive. Who would ever want to steal it? It's too easy to identify and that's a big plus in my neighborhood.

 

[CatSquare]

Super cool, nice work on that.

 

[gumtown]

The replacement amplifier module turned up the other day, it is now installed and tested.
This new Class D amp runs a lot cooler then the first amp (traditional class A/B), and takes up a bit less space too.

L15D X2 Top Class D Stero Amplifier Board IRS2092 IRAUDAMP7S 125W 500W CL100 | eBay

The module is a stereo pair, here is the schematic of one channel

Just waiting now on the 100w Horn amp to arrive and build an active crossover - I have a good Linkwitz-Riely 24db/octave circuit for that.

 

[gumtown]

Gigged the combo with the new Class D amp last night, and it went GREAT !!!
Still needed to use my Tech21 Vt-Bass pedal to boost the 'character' mids, so I might tweak the tone section to boost that particular freq range.

Plenty of volume to use on it's own for a small bar gig, and a few comments on how good it sounds.

 

[MarkA]

Cool!