Okay, here we go. Some very quick measurements.
Beyerdynamic MM1 with a Behringer USB interface.
Red: close-mic'd driver (right in where the dustcap meets the cone)
Green: port
Purple: 1" away from baffle, between edge of driver and port
Yellow & blue: 1' away, centred between driver and baffle.
I think a touch of EQ to bring the bottom end will be in order, but this looks pretty good from the off. Adjusting Hornresp sims to give a 34Hz tuning (made the lengths a little longer, and made some of the areas a little smaller) gives a response that looks very similar.
Haven't done any serious listening yet, since there's company at the moment. Maybe tomorrow.
Chris
Beyerdynamic MM1 with a Behringer USB interface.
Red: close-mic'd driver (right in where the dustcap meets the cone)
Green: port
Purple: 1" away from baffle, between edge of driver and port
Yellow & blue: 1' away, centred between driver and baffle.
An externally hosted image should be here but it was not working when we last tested it.
I think a touch of EQ to bring the bottom end will be in order, but this looks pretty good from the off. Adjusting Hornresp sims to give a 34Hz tuning (made the lengths a little longer, and made some of the areas a little smaller) gives a response that looks very similar.
Haven't done any serious listening yet, since there's company at the moment. Maybe tomorrow.
Chris
Okay, so EQ applied: 35Hz, +4dB, Q=2. Looks pretty flat on REW's EQ simulator.
Think I'm gonna keep it. Its just over twice the size of the sealed boxes I'm using at the moment, but it'll hit every note of this: https://www.youtube.com/watch?v=-Po2746MdDY with plenty of authority. Good enough for me - if someone says "go on, play something with bass", that's my go-to. This cab passes that test just fine.
Listening to some other music now, and its rather good. Got a Behringer B3030A sat on top, XO at 100Hz and the EQ at the top of this post. This sub doesn't stick out, just extends what the Behringer does by another octave.
I'm not gonna go into all the audiophile speak. This is a very nice driver in a cabinet that loads it well, and that's what it sounds like.
Chris
Think I'm gonna keep it. Its just over twice the size of the sealed boxes I'm using at the moment, but it'll hit every note of this: https://www.youtube.com/watch?v=-Po2746MdDY with plenty of authority. Good enough for me - if someone says "go on, play something with bass", that's my go-to. This cab passes that test just fine.
Listening to some other music now, and its rather good. Got a Behringer B3030A sat on top, XO at 100Hz and the EQ at the top of this post. This sub doesn't stick out, just extends what the Behringer does by another octave.
I'm not gonna go into all the audiophile speak. This is a very nice driver in a cabinet that loads it well, and that's what it sounds like.
Chris
Hi Oliver,
Some pictures coming shortly.
For now, here's an impedance plot to contemplate. All looks fine, except the impedance drop past 8kHz. Doesn't show up on the manufacturer's datasheet, and the impedance calibration went just fine, ruler-flat at 102ohm. Very weird. The drop showed up repeatably, which is why I mention it.
My NU6000DSP has died completely, so I'm using one side of an EP1500 for now. Not seriously cranked it up, but there's wall-shaking capability here. Without reaching full power (which is only a few hundred watts), the house (old, heavy stone walls) was starting to complain a little.
I'll go and take those pictures.
Cheers
Chris
Some pictures coming shortly.
For now, here's an impedance plot to contemplate. All looks fine, except the impedance drop past 8kHz. Doesn't show up on the manufacturer's datasheet, and the impedance calibration went just fine, ruler-flat at 102ohm. Very weird. The drop showed up repeatably, which is why I mention it.
An externally hosted image should be here but it was not working when we last tested it.
My NU6000DSP has died completely, so I'm using one side of an EP1500 for now. Not seriously cranked it up, but there's wall-shaking capability here. Without reaching full power (which is only a few hundred watts), the house (old, heavy stone walls) was starting to complain a little.
I'll go and take those pictures.
Cheers
Chris
Not quick enough to get in before the Edit window closes.
Just a quick one:
Chris
Just a quick one:
An externally hosted image should be here but it was not working when we last tested it.
Chris
Zmin comes in at 7.8ohm at 37Hz.
Phase passes through zero at 37Hz, though the cone excursion dip comes in a tad lower, at 34Hz. Getting the impedance peaks to match up in Hornresp gives a ~35Hz cone excursion dip. Looks like simulations and reality are working pretty closely here.
Chris
Hi chris661,
Nice clean looking build, you are turning into a woodworm.
I haven't seen a similar drop in the high frequency impedance as shown in Post #46. The normal distributed/interlayer capacitance for a woofer would be much smaller than the inductance, so there should not be a drop, just a steady increase?
Regards,
Nice clean looking build, you are turning into a woodworm.
I haven't seen a similar drop in the high frequency impedance as shown in Post #46. The normal distributed/interlayer capacitance for a woofer would be much smaller than the inductance, so there should not be a drop, just a steady increase?
Regards,
Here was my answer to this question:
http://www.diyaudio.com/forums/subw...ct-ported-15-dayton-ref-ho-8.html#post3427597
They now have nice B&C woofers in them, and still crush it.
Just out of curiousity, which version of 15P1200Nd is this? I've seen a few different sets of specs for this driver. Which is the correct spec sheet?
...
Messing about with some different specs, the end result seems relatively similar on the different versions, phase looks really good.
This is just for fun, port length can be varied greatly.
It's very deep, basis of calculation was 60cm internal depth by 44cm width, front is relatively compact, but it's not a very lightweight design ca 150 liters.
...
Messing about with some different specs, the end result seems relatively similar on the different versions, phase looks really good.
This is just for fun, port length can be varied greatly.
It's very deep, basis of calculation was 60cm internal depth by 44cm width, front is relatively compact, but it's not a very lightweight design ca 150 liters.
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Good question about which driver version. I honestly don't know.
I bought the drivers in two pairs from different (2nd hand) suppliers. None of them have the original Beyma sticker on the back. All of them are identical, and look very similar to the photos produced by Beyma. I'll check the weight, too - I think that'll be a good indicator.
I haven't noticed any difference in performance between them, but now that I can measure impedance, I'll try the added mass method and make sure they're all close to each other, and to factory specs.
Turbo, those are some nice looking cabs. I've followed your thread for a while. Shame about the DJs, it's getting rare to find a good one that won't redline everything these days.
Oliver, the impedance drop showed up repeataby, and it's not something I've seen before, which is why I thought I'd mention it.
When I'm measuring the T/S parameters, I'll see if it shows up again. It's very weird.
Chris
I bought the drivers in two pairs from different (2nd hand) suppliers. None of them have the original Beyma sticker on the back. All of them are identical, and look very similar to the photos produced by Beyma. I'll check the weight, too - I think that'll be a good indicator.
I haven't noticed any difference in performance between them, but now that I can measure impedance, I'll try the added mass method and make sure they're all close to each other, and to factory specs.
Turbo, those are some nice looking cabs. I've followed your thread for a while. Shame about the DJs, it's getting rare to find a good one that won't redline everything these days.
Oliver, the impedance drop showed up repeataby, and it's not something I've seen before, which is why I thought I'd mention it.
When I'm measuring the T/S parameters, I'll see if it shows up again. It's very weird.
Chris
So, the HF impedance drop remained consistent, and of course meant REW threw a hissy fit when calculating T/S parameters, since it expects a rising impedance up to 20kHz. I've only tested this one driver, so we'll see what the rest do.
Ran the sweeps up to 6kHz, however, and it was fine again. Put the new T/S parameters into Hornresp, and we're looking at ~0.1dB changes in the low end. Pretty negligible if you ask me.
Haven't weighed them yet, that's on the to-do list.
Chris
PS - measured T/S:
Fs: 38.7Hz
Qms: 10.56
Qes: 0.237
Qts: 0.232
Vas: 123L
BL: 27.64 Tm
Cms: 0.119mm/N
Mms: 142.75g
SPL: 96.83dB @1w
Re: 5.22ohm
Le: 1.7mH
Sd: 855cm^2, per datasheet
Ran the sweeps up to 6kHz, however, and it was fine again. Put the new T/S parameters into Hornresp, and we're looking at ~0.1dB changes in the low end. Pretty negligible if you ask me.
Haven't weighed them yet, that's on the to-do list.
Chris
PS - measured T/S:
Fs: 38.7Hz
Qms: 10.56
Qes: 0.237
Qts: 0.232
Vas: 123L
BL: 27.64 Tm
Cms: 0.119mm/N
Mms: 142.75g
SPL: 96.83dB @1w
Re: 5.22ohm
Le: 1.7mH
Sd: 855cm^2, per datasheet
Chris,
The response is dropping at 6 dB per octave from 100 Hz to 50 Hz, then really goes south. Measuring combined response of port and radiator at only 1 foot is a little "iffy", but may be "close enough for rock & roll" ;^) .
We seem to differ in our opinion of what a "touch of EQ" is (by an order of magnitude), but for PA work, you either must go big, or higher tuning, or use a boatload of power and EQ to achieve rock & roll LF.
Having been quite underwhelmed by the performance of the ported PPSL "Shoehorn" dual 15" cabinets, which had an even more severe LF "droop" than yours (and add way too much harmonic distortion when brought up to flat, as well as releasing far too much heated epoxy stink, while being about 6 dB short of the Keystone using half the power...) , it's back to "real" sized cabinets for me.
Just have to figure out where to store them, I can only easily fit a pair in my PA trailer, and the backyard shed of my rental house has an army of termites surrounding it, they would be ready to eat the other four, like they did the Keystone cardboard templates...
Cheers,
Art
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Venting...
So, I've just subject one of my nice drivers to >500w of VLF sine waves.
I was running some sweeps 10Hz-400Hz at low levels, changed the lower cutoff to 30Hz, and ran some high-level sweeps.
There were some loud farting noises, and the cone now has a few fold lines. It also feels quite bendy.
Turns out that, while it only plots the graph from 30Hz upwards, 10Hz still comes out of the soundcard, sometimes. I can't find the pattern, but the sweep frequencies don't always change.
Bother.
Actually, bother doesn't really cover it. Never mind. Expensive mistake, though.
The driver still sounds okay, but I really don't trust it. Enquiring about a recone job at a UK supplier, but it won't be cheap. The folds appear to only be on the surface of the cone.
I might see how this driver holds up to high-power sine wave testing, since its already a bit knackered.
So yes, driver exposed to 10Hz at -6dB on an NU6000. Cone has folds on the outside, but not inside. What does the panel think?
Recone or live with it?
Chris
So, I've just subject one of my nice drivers to >500w of VLF sine waves.
I was running some sweeps 10Hz-400Hz at low levels, changed the lower cutoff to 30Hz, and ran some high-level sweeps.
There were some loud farting noises, and the cone now has a few fold lines. It also feels quite bendy.
Turns out that, while it only plots the graph from 30Hz upwards, 10Hz still comes out of the soundcard, sometimes. I can't find the pattern, but the sweep frequencies don't always change.
Bother.
Actually, bother doesn't really cover it. Never mind. Expensive mistake, though.
The driver still sounds okay, but I really don't trust it. Enquiring about a recone job at a UK supplier, but it won't be cheap. The folds appear to only be on the surface of the cone.
I might see how this driver holds up to high-power sine wave testing, since its already a bit knackered.
So yes, driver exposed to 10Hz at -6dB on an NU6000. Cone has folds on the outside, but not inside. What does the panel think?
Recone or live with it?
Chris
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