Something Stirs in the Workshop

[steve s]

Not audiophile spikes then steve !
Like it..

[vinylnvalves]

The spikes are pure audiophile - chineseium known for its excellent damping properties and poor strength….

[vinylnvalves]

Just started making a test horn ( 1.4”) for open baffle speaker project.. for someone. The rear section, quite fiddly as have to do it in multiple sections, to get a flange to mount the horn too. Will finish the mouth when I get back after a weeks break.

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[MistyBlue]

Awesome stuff as ever.

I could do with a cnc wood router about now!

[steve s]

Nice workmanship as ever steve..

[vinylnvalves]

Just finished the test horn, shipping it out for evaluation. Bit trickier than first thought as had to recontour the inner after a late change in throat angle, plastic wood filler to make the inner match, as cannot add wood. Not my finest work, as cobbled together out of the firewood box, and glued out of lots of bits
(Also trimmed 5mm off the width to make it fit in a box ). It sims a lot better than those ES horns I built before. It’s 395x 320mm. Slightly truncated as that was the biggest piece of scrap I had lying about.

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[chris661]

Looks the business, Steve. Got any specs?

The size looks like the right sort of thing for these BMS 2" drivers that were on plastic horns at Owston.


Chris

[vinylnvalves]

They are for 1.4” drivers - matched the throat angle for the SB Rosso driver. Chris, I can send you the AKABAK input files for a 2” version if you want.. I haven’t got my head around running AKABAK yet, it’s alien to me

[vinylnvalves]

Saw an article about time aligning drivers with a impulse response... so i had a play in Holm impulse.

Tried time aligning the sub to the bass driver - both are effectively sealed, so wasnt expecting an massive difference in group delay. The plots would suggest otherwise, The blue trace is the sub. The red and green are the bass driver, i tried delaying the signal by 0.2ms with the green trace to see if it was doeing as expected- which it did. Cannot believe i need to delay the subwoofer by 4.5 millseconds to align. That almost 1.5m of delay. Chris..... what am i doing wrong?

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[brig001]

What are you using for a crossover, and what frequency are you crossing over?

Brian

[Morgan Jones]

4.5ms sounds perfectly plausible to align something to a subwoofer. You have a low-pass filter that adds a lot of delay, plus a little from the low-pass response of the driver itself.

[vinylnvalves]

I have a 2nd order LR at 120 Hz, for the sub, crossing with the low mid which covers upto 1600hz. All active crossovers

[chris661]

Yep, looks like we're dealing with time alignment once crossover slopes are in play.
If you've got REW working, I read somewhere that using tone bursts while watching the results on the 'scope are a good way to see what's going on.


I can't remember the capabilities of the DSP you're using, but it can be interesting to throw a load of FIR around, and get the system impulse-perfect.


Chris

[vinylnvalves]

I am using IIR filters as I am running out of processor power, with 8 channels. I obviously assumed wrongly that the delay would be constant across all channels, so the time differences between channels wouldn’t be considerable.

[chris661]

Processing latency will be identical. Phase shift due to crossover slopes will vary according to the crossover slope.

NB - phase is just time expressed as a function of frequency.


Chris