Another budget driver option?

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joblow88
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Re: Another budget driver option?

#16 Post by joblow88 »

So i took one for the team and i bought a GRS 15PT-8 https://www.parts-express.com/GRS-15PT- ... hm-292-808 and i plan to test it in my soon to be finished t48. I was wondering if there was a way to stress test the cone strenght once in the cab without angrying the whole neighborhood. I was thinking maybe a lower frequency at the right voltage would create the same throat pressure... I'm also planing to run at rms power out of the cab for an extended period of time to look at the thermals.

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Seth
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Re: Another budget driver option?

#17 Post by Seth »

Just off the top of my head, a purely speculative educated guess based on my (questionable) logic... it makes sense to me that throat pressure would be highest at the resonant frequency, where electrical impedance is lowest and acoustic impedance is highest.

@Bill, Is that accurate?

If so, modeling that driver in my SketchUp derived version of the T48 indicates 42Hz would hive the highest throat pressure.

You're likely to drive your whole neighborhood nuts at that frequency. Let me know how that goes :D

How wide are you building?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bill Fitzmaurice
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Re: Another budget driver option?

#18 Post by Bill Fitzmaurice »

Throat pressure will be highest where excursion is highest. As is the case with ported enclosures that coincides with where electrical impedance is highest, while excursion is lowest where impedance is lowest.

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Seth
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Re: Another budget driver option?

#19 Post by Seth »

I got it backwards. Thank you :thumbsup:

In my model, it indicates the greatest excursion occurs at roughly 25Hz. Would it matter if it's not within the horn's pass band? Or, is it the highest excursion within the horn's pass band?
Last edited by Seth on Fri Sep 23, 2022 5:07 pm, edited 1 time in total.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bill Fitzmaurice
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Re: Another budget driver option?

#20 Post by Bill Fitzmaurice »

We high pass and limit so that the driver isn't stressed. A side benefit is that abnormally high throat pressure, which causes distortion, doesn't occur.

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Seth
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Re: Another budget driver option?

#21 Post by Seth »

For normal usage, yes. And it has worked brilliantly.

It appears he'd like to test the cone durability in a manner that is outside the bounds of the recommended settings. Which, I agree is not a good idea unless he's 100% completely willing to damage the driver.

Perhaps it's not a bad idea to just test at the point of highest excursion within the bounds of the recommended high pass settings, which looks to occur at 57Hz on 41.8 volts. Gonna be super loud though, ±125db (based on my full 36" wide cab model).

Where, if it still creates the high throat pressures even though it's outside the horns pass band, the same 6.8mm excursion would occur at 25Hz on only 17 volts and have an output of about 105dB, which is obviously way more manageable for a long term stress test (IMO). But, the question remains, would it still achieve high throat pressures since it's a frequency that's technically not horn loaded? I wanna say no, it wouldn't. But, I've been wrong before. LOL
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

joblow88
Posts: 57
Joined: Sun Feb 13, 2022 8:18 pm

Re: Another budget driver option?

#22 Post by joblow88 »

Seth wrote: Fri Sep 23, 2022 5:33 pm

Where, if it still creates the high throat pressures even though it's outside the horns pass band, the same 6.8mm excursion would occur at 25Hz on only 17 volts and have an output of about 105dB, which is obviously way more manageable for a long term stress test (IMO). But, the question remains, would it still achieve high throat pressures since it's a frequency that's technically not horn loaded? I wanna say no, it wouldn't. But, I've been wrong before. LOL
Yup that was exacly my thinking. Create the max throat pressure the driver would get exposed to (57Hz on 41.8 volts so it seems) without blasting 135+db for multiple hours. If it end up living it's a good deal.

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Seth
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Re: Another budget driver option?

#23 Post by Seth »

joblow88 wrote: Fri Sep 23, 2022 8:24 pm Yup that was exacly my thinking.
How wide are you building your T48?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

joblow88
Posts: 57
Joined: Sun Feb 13, 2022 8:18 pm

Re: Another budget driver option?

#24 Post by joblow88 »

19" outside 18 inside

joblow88
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Re: Another budget driver option?

#25 Post by joblow88 »

Seth wrote: Fri Sep 23, 2022 8:52 pm
joblow88 wrote: Fri Sep 23, 2022 8:24 pm Yup that was exacly my thinking.
How wide are you building your T48?
19" outside 18 inside

joblow88
Posts: 57
Joined: Sun Feb 13, 2022 8:18 pm

Re: Another budget driver option?

#26 Post by joblow88 »

Anyone??

Bruce Weldy
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Re: Another budget driver option?

#27 Post by Bruce Weldy »

joblow88 wrote: Thu Sep 29, 2022 6:40 pmAnyone??
Might want to re-state the question....I couldn't figure out what you're looking for.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Seth
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Re: Another budget driver option?

#28 Post by Seth »

Yeah, I'm scratching my head over here. Thought we sorted it out. Anyone what?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

joblow88
Posts: 57
Joined: Sun Feb 13, 2022 8:18 pm

Re: Another budget driver option?

#29 Post by joblow88 »

Yeah i guess my questions are not the mos clear. Sorry
1 Does running the cab at 25Hz @ 17v is going to recreate the the highest throat pressure that what my speaker would be exposed to in normal use (57Hz on 41.8 volts according to Seth) even if it is out of the frequency range of the cab?
2 Since seth number come from his simulation of a 36'' wide cab can i transfer theses number to my 19'' wide cab?
my cab is a t48 x 19''
Thanks a lot

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Seth
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Re: Another budget driver option?

#30 Post by Seth »

It's not likely at all that Bill will consider recommending anything outside the stated limits of the enclosure.

I'd say, if you wanna try it, try it. If it's not actually loaded the same as if it were a frequency within the designed bandwidth, so what.

My guess is that driver will do just fine and will be reliable if the appropriate high pass and voltage limits are applied and active. I went ahead and modeled a 19" (18" internal) T48 and 41.8v stays true as a max voltage although the peak excursion within it's bandpass has moved to 59Hz.

If you choose to try it outside it's recommended limitations, in a 19" wide T48 with that driver, 13.4v at 20Hz will get you to the drivers Xmax of 6.8mm and should only be about 99dB. An even more manageable volume and frequency combination. You, or the neighbors, wont hear a thing except nearby stuff rattling.

How do you intend to use the cab normally? Live music? DJ? What sort of events and venues?

Oh, and... thanks BTW, for taking one for the team :thumbsup:
Last edited by Seth on Sun Oct 02, 2022 3:01 pm, edited 1 time in total.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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