Bill Fitzmaurice wrote: ↑Fri Jun 02, 2023 8:45 pm
I wouldn't recommend that, it doesn't model well at all. There's no point in very long xmax when you don't have the power to make use of it.
Interesting. The specs are within stated parameters. Do you know off hand if the Qts near the upper limit, Fs near the lower limit, or the combination of the two that causes it to not model well?
I really like knowing you run the numbers on these drivers that get posted.
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Seth wrote: ↑Fri Jun 02, 2023 8:54 pm
Do you know off hand if the Qts near the upper limit, Fs near the lower limit, or the combination of the two that causes it to not model well?
It's the combination of the two. Where all of the specs are concerned it's best to be in the middle of the range. With horns you always get the best result when Fs is at or higher than the horn corner frequency. Making the rear chamber smaller when Fs is low helps, but the combination of low Fs and high Qts can't be compensated for.
Bill Fitzmaurice wrote: ↑Sat Jun 03, 2023 7:32 am
...Where all of the specs are concerned it's best to be in the middle of the range. With horns you always get the best result when Fs is at or higher than the horn corner frequency. Making the rear chamber smaller when Fs is low helps, but the combination of low Fs and high Qts can't be compensated for.
One of the most insightful posts I've read. Thank you Bill.
Two follow up questions, if I may
1) What was it about the model of that driver that was insufficient? Extension, sensitivity, both, something else?
2) What about the other way around? A driver with Fs on the high end high and Qts on the low end? What effect does that have on the response curve?
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The response wasn't at all smooth, with unacceptable peaks and valleys. High Fs and low Qts gives better sensitivity at the upper end, at the cost of the low end. That's not necessarily a problem with a top, it can even be advantageous, but you don't want it in a sub.
Hmm I think that level of parameters detail is beyond me at this point. Hopefully one day.
That modeling badly GRC driver is anyway not easily available to me here in the UK, neither is the dayton suggestion (although thanks for the suggestions!). The eminence delta 12 L FC Is available here but isn't cheap. Two of them cost just a bit more then one of the kappalite 3015lfs.
Im thinking perhaps I should build with the intention to upgrade the amp. And get the most out of my box.
I guess I'm asking would the t48 loaded with a single 3015lf with that amplifier far out perform the two eminence 12s seth suggested with my current amplifier?
Maybe this isn't the best place to ask basic speaker wiring questions but I'm still struggling to fully understand the functions behind Seth's suggestion of running two 12s as a solution to my weak amp:
Bruce Weldy wrote: ↑Sat Jan 08, 2022 4:31 pm
Use the 8 ohm version of the driver. Then you don't have to change the crossover specs.
thanks for the reply,
Will this not be underpowered by the amp channel I have available for it?
No, it doesn't work that way. Speakers see voltage, not watts. 40 volts at 8 ohms will measure 200 Watts. 40 Volts at 4 ohms will measure 400 Watts. But either speaker at 40 volts will produce the same volume. The 8 ohm version of the driver you specified will be just as loud, but you won't have to try to change the passive crossover that's in the plans.
And yes, a Jack 15 would most likely give you what you want in a single cab with less expense.
This was Bruce's point on a different 12v thread. If Bruce is correct. Does this mean twinning the 12s as seth is now suggesting is beneficial ONLY because their combined output is greater than a single 15 based on combined sensitivity? Because if I follow Bruce's logic it seems getting it down to 2ohms impedance (wiring in parelel) doesn't turn my weak amps potential voltage into more output per se...
Is this correct or am I still missing someing basic?
An amp will put out the same voltage into any impedance load. Excursion, which determines output, with a constant voltage goes up as impedance goes down. Therefore the lower the impedance the higher the output with any given amp. But current also goes up as impedance goes down. Too much current draw will damage the amp, so you can't use a load lower than what the amp is rated for.
I'm weighing up your solution To the smaller amp problem - the low ohms twin 12s setup and pitting it against building with a 3015lf with intention of amp upgrade later. Here's my mental list of pros on either side ... please do correct me if any of them are built on a fallacy :
Twin 12s:
cheaper. (no need to buy amp)
Higher output immediately with current setup.
On the other hand 3015lf:
Same price now, but lower output. more expensive overqll including amp upgrade cost.
Eventually higher output when amp is upgraded.
More versatility (can be used better in other setups, powered by normal mains electricity etc)
Buy once, cry once. You can't beat the 3015LF. If you find that you need a larger amp to get the most out of it cross that bridge when you get to it. Never having experienced a T48 with even a 50w amp you have no idea what it's capable of. If you're like 99% of those who've built them you'll be more than pleasantly surprised.
I'm weighing up your solution To the smaller amp problem - the low ohms twin 12s setup and pitting it against building with a 3015lf with intention of amp upgrade later. Here's my mental list of pros on either side ... please do correct me if any of them are built on a fallacy :
Twin 12s:
cheaper. (no need to buy amp)
Higher output immediately with current setup.
On the other hand 3015lf:
Same price now, but lower output. more expensive overqll including amp upgrade cost.
Eventually higher output when amp is upgraded. Not necessarily. In many cases, two 12's offer more potential peak output than a single 15. Depending on the specific 12's in question, you could possible end up with essentially the same output potential with without having to upgrade the amp
More versatility (can be used better in other setups, powered by normal mains electricity etc) Excellent point! Yes, correct. Although, using two 8 Ohm 12's wired in parallel would maintain this versatility. It would still need an amp upgrade to get the most out of the drivers, but you would only need something that puts out 450-500w continuous at 4 Ohm. Where, with a single 8 Ohm driver you'll need an amp that can provide 900-1000 watts continuous at 4 Ohm.
Last edited by Seth on Sun Jun 04, 2023 11:32 am, edited 1 time in total.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded
Bill Fitzmaurice wrote: ↑Sun Jun 04, 2023 7:36 am
Buy once, cry once. You can't beat the 3015LF. If you find that you need a larger amp to get the most out of it cross that bridge when you get to it. Never having experienced a T48 with even a 50w amp you have no idea what it's capable of. If you're like 99% of those who've built them you'll be more than pleasantly surprised.
In this application, would you recommend a single 3015LF over a pair of 3012LF's?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded