What would you do with these drivers?

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vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Fri Jan 08, 2021 4:36 pm

Started machining the H frame for these drivers. Having to recycle some 15mm chipboard, hopefully will have enough- starting to feel like Mark recycling material, gluing bits together to make larger bit, but I cannot pop down the lumberyard currently. Unlike Marks all my failed builds end up on the fire.. generating some useful heat
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simon
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Re: What would you do with these drivers?

Post by simon » Fri Jan 08, 2021 4:42 pm

CNC - that's cheating :-D

vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Fri Jan 08, 2021 6:01 pm

Cheating using CNC... oh yes. Only to get the bolt hole pattern correct. Strangely the mounting holes are 5.3mm so critical to ensure the mounting holes are close enough to get all 8 m5 insets to line up per driver.

vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Mon Jan 11, 2021 4:59 pm

Finished my recycled test cabinet, ended up using MDF, oak off cuts as well as chipboard. Wired up the two drivers independently, each will get 450watts.
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(Apologies for the clutter - working from home means the music room has to double up as an office and the stuff I stored behind the sofa has ended up in front to make way for a desk)

The next question how do you measure subwoofers indoors. Cannot see any point dragging it outside as the room gain will dominate the FR. I have determined how they theoretically will respond in the H frame. The emphasis curve to plug in the DSP isn’t that dissimilar from the one supplied for the LX 521’s so I won’t be a million miles out if the room gain isn’t big.

chris661
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Re: What would you do with these drivers?

Post by chris661 » Mon Jan 11, 2021 11:06 pm

Well, I'd say the subwoofer + room combination is what ought to be measured. Give it a go, see what's what.

Chris

vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Tue Jan 12, 2021 5:40 pm

Right had a play this afternoon after work... near field measurements in front of each cone and 1m away. ( Sorry for poor quality pics measurements laptop doesn’t have internet so photos of screen I’m afraid)
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Then here is the combined FR trace with phase...
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The signal was rolled off at 500 hz, with a 9 db low shelf from 70 Hz to boost the bottom. The Linkwitz transform for the LX521’s has significantly more LF boost than I have applied.

I did one measurements without any attenuation of the signal... I can verify the cones move with 400 watts at 10Hz, not the 52mm P-P they are capable off around half what, not pleasant, when your not wearing ear defenders.

Not sure what I was expecting I get flat to 50 Hz from the Supravox drivers with an f6 of 30Hz so. The Supravox aren’t flat from 100hz to 400hz due to room interactions though.

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Re: What would you do with these drivers?

Post by IslandPink » Wed Jan 13, 2021 10:16 am

Interesting - so what was the LP on the subwoofers ?
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vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Wed Jan 13, 2021 10:25 am

IslandPink wrote:
Wed Jan 13, 2021 10:16 am
Interesting - so what was the LP on the subwoofers ?
LP??

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Re: What would you do with these drivers?

Post by IslandPink » Wed Jan 13, 2021 12:09 pm

Low Pass
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vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Wed Jan 13, 2021 12:39 pm

The LP was @500Hz, 2nd order linkwitz. Only set it there for testing, the H frame simulator would suggest I get some driver interaction around 260Hz. The intended crossover will be around 120 Hz, if I decide to go away from my 3 way to a 4 way. In the FIR crossover world LP filters are less computationally expensive than HP filter. Will play later but a LP filter maybe 2nd order from 30Hz may give the LF profile I need for a flat response. The midbass drivers I would use instead of the Supravox’s have an F3 of 120 Hz , so would try to use the natural roll off of that driver.

It’s hard to tell what they will sound like from measurements, want some confidence before ripping down the existing setup to make all the necessary changes. I might run it upto 350Hz replacing the Supravox in the existing setup to see if the low end is any better first. I will have to somehow account for the poorer response around 300 Hz though, which is hard as the harmonics affect the LF response.

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Re: What would you do with these drivers?

Post by vinylnvalves » Wed Jan 13, 2021 5:41 pm

Just tried reconfigured the input signal so it looks like this, it’s basically a 2nd order LP from 1 Hz.
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Here is the frequency response compared to the response from yesterday. So in theory you could equalise the response using a low pass crossover with a capacitor and inductor. But your going to need a 1000mH inductor :)
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Re: What would you do with these drivers?

Post by steve s » Wed Jan 13, 2021 6:22 pm

vinylnvalves wrote:
Wed Jan 13, 2021 12:39 pm


It’s hard to tell what they will sound like from measurements, want some confidence before ripping down the existing setup to make all the necessary changes. I might run it upto 350Hz replacing the Supravox in the existing setup to see if the low end is any better first. I will have to somehow account for the poorer response around 300 Hz though, which is hard as the harmonics affect the LF response.
No easy way but to try it steve..
I found the bass drivers I use lacking once you get to 200-300hz or so.
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Re: What would you do with these drivers?

Post by vinylnvalves » Wed Jan 13, 2021 6:58 pm

I don’t think the driver will be lacking at 300Hz SEAS use it in a speaker above that, it’s the H frame is only designed to work upto around 260 Hz above that front waves and rear waves combine and it goes to pot. I have ordered another xlr lead so I can plug in another channel, that will allow me to use it as it should be, abiet using the Supravox to only cover 100hz to 350hz.. not the best use of a 15” though

vinylnvalves
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Re: What would you do with these drivers?

Post by vinylnvalves » Wed Jan 13, 2021 7:03 pm

Yes an 18” speaker is only good for 250 Hz putting beaming aside

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Re: What would you do with these drivers?

Post by simon » Wed Jan 13, 2021 7:22 pm

vinylnvalves wrote:
Wed Jan 13, 2021 6:58 pm
the H frame is only designed to work upto around 260 Hz above that front waves and rear waves combine and it goes to pot.
That's interesting. I hadn't considered this phenomenon before, what's happening? I can't quite work it out, is it something to do with delay of the rear wave coming back off the rear wall?

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