I suspect a few reasons for putting the ports on the front:
1 - you can mount them against a wall, no problem.
2 - you can hide them behind grilles to stop crap getting in
3 - midrange leakage
According to WinISD, the first port resonance of a 3" port this length will be 850Hz. I'm crossing over very close to that, 800Hz. An out-of-band notch might help.
I'll measure with REW to see what the ports are actually doing. There's lots of bracing in there, and the backs of the drivers aren't that open, so I might just get away with it. The graphs will come once the cabs are finished and everything's mounted with foam gaskets. If its a serious problem, I'll consider crossing over even lower. I think, if anything, a higher crossover might help match directivity between the HF and 10"s, but we'll see how that goes.
The gig the other night was an exercise in taking as little PA as possible, while still getting a decent full-range sound. Ended up with a pair of 8" coaxials on stands, another pair as monitors, and a pair of the 15" subs. Took the crossover up to 200Hz to try to make sure the 8"s wouldn't struggle too much. NU3000DSP for tops and monitors, NU6000DSP for subs. The whole setup was mono, since the speakers would be close together.
Venue was a pub with an odd layout, probably around 50 people in there.
Everything was loud enough - just. I set the subs aiming for 40Hz, and got a really nice deep punch out of them. Towards the end of the night, things got quite loud and both the tops and the subs were nudging into clip. The sound didn't suffer noticably, but I didn't push any further.
I'm hoping that running the subs up to 80Hz-ish instead of 200Hz will give them a bit more headroom - they sounded good, but I can see them being the limiting factor in sheer output later on.
Last night at work I took a fair chuck off my left index finger, so that's all bandaged up. Fortunately, I'm right-handed, so I'm still making progress on these cabs. I've just run around with a flush trim router, and they already look miles better.
Chris
1 - you can mount them against a wall, no problem.
2 - you can hide them behind grilles to stop crap getting in
3 - midrange leakage
According to WinISD, the first port resonance of a 3" port this length will be 850Hz. I'm crossing over very close to that, 800Hz. An out-of-band notch might help.
I'll measure with REW to see what the ports are actually doing. There's lots of bracing in there, and the backs of the drivers aren't that open, so I might just get away with it. The graphs will come once the cabs are finished and everything's mounted with foam gaskets. If its a serious problem, I'll consider crossing over even lower. I think, if anything, a higher crossover might help match directivity between the HF and 10"s, but we'll see how that goes.
The gig the other night was an exercise in taking as little PA as possible, while still getting a decent full-range sound. Ended up with a pair of 8" coaxials on stands, another pair as monitors, and a pair of the 15" subs. Took the crossover up to 200Hz to try to make sure the 8"s wouldn't struggle too much. NU3000DSP for tops and monitors, NU6000DSP for subs. The whole setup was mono, since the speakers would be close together.
Venue was a pub with an odd layout, probably around 50 people in there.
Everything was loud enough - just. I set the subs aiming for 40Hz, and got a really nice deep punch out of them. Towards the end of the night, things got quite loud and both the tops and the subs were nudging into clip. The sound didn't suffer noticably, but I didn't push any further.
I'm hoping that running the subs up to 80Hz-ish instead of 200Hz will give them a bit more headroom - they sounded good, but I can see them being the limiting factor in sheer output later on.
Last night at work I took a fair chuck off my left index finger, so that's all bandaged up. Fortunately, I'm right-handed, so I'm still making progress on these cabs. I've just run around with a flush trim router, and they already look miles better.
Chris
There's a couple of reasons I ruled out triangular ports early on:
Not enough port area - the 4x 3" round ports are very marginal as-is.
Attaching the grilles would also get more difficult, since it'd wipe out the last bit of baffle area I can screw anything to.
Cutting 45-degree chamfers would also present problems, though it might be possible with the router, a 45-degree roller bit, and even more clamps.
For what its worth, these will be used almost exclusively for live sound, with stage monitors present. I'm going to see how the round ports go first. I think they'll be absolutely fine, but testing will reveal all - if it turns out they're very problematic, I'll rebuild with triangular ports.
Chris
Not enough port area - the 4x 3" round ports are very marginal as-is.
Attaching the grilles would also get more difficult, since it'd wipe out the last bit of baffle area I can screw anything to.
Cutting 45-degree chamfers would also present problems, though it might be possible with the router, a 45-degree roller bit, and even more clamps.
For what its worth, these will be used almost exclusively for live sound, with stage monitors present. I'm going to see how the round ports go first. I think they'll be absolutely fine, but testing will reveal all - if it turns out they're very problematic, I'll rebuild with triangular ports.
Chris
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So, I've got the pair of them stained and up and running.
Still no testing done, just an LR4 crossover at 800Hz, and some approximate time-alignment (3.5ms delay on the mids).
I have to say, these sound very very good. I've been playing music all evening, and noticing all sorts of things on tracks that I thought I knew. For example, Toy Soldiers by Eminem has patches of double-tracked vocals. Bjork's It's Oh So Quiet was very fun to listen to, and I still have chills from Hello by Evanescence.
I've only been using a pair of subs tonight, EQ'd down to 20Hz. I'd like some bigger, meaner cabs for these drivers at some point, but for now, for the gigs I'm doing, these are good.
Got a big gig (for me) coming up on the 17th - 3 bands, one of which is launching their EP. Plenty of setup time, so I'll be taking my time to get things sounding really nice - very much looking forward to it.
Chris
Still no testing done, just an LR4 crossover at 800Hz, and some approximate time-alignment (3.5ms delay on the mids).
I have to say, these sound very very good. I've been playing music all evening, and noticing all sorts of things on tracks that I thought I knew. For example, Toy Soldiers by Eminem has patches of double-tracked vocals. Bjork's It's Oh So Quiet was very fun to listen to, and I still have chills from Hello by Evanescence.
I've only been using a pair of subs tonight, EQ'd down to 20Hz. I'd like some bigger, meaner cabs for these drivers at some point, but for now, for the gigs I'm doing, these are good.
Got a big gig (for me) coming up on the 17th - 3 bands, one of which is launching their EP. Plenty of setup time, so I'll be taking my time to get things sounding really nice - very much looking forward to it.
Chris
Got the measurement mic out, and took everything outside. Nearest reflective surface was around 10' behind the speakers, bottom of the cab 4' off the grass.
The initial graphs were okay, but it turned out I'd done a brain fart and delayed the tweeter instead of the 10"s, giving a weird dip/peak around 900-1kHz and lots of exciting phase angles.
Corrected that, and re-addressed the relative SPLs of the woofers and tweeters, and got the following:
Then, with a bit of averaging and smoothing:
Not bad!
I ran the Auto-EQ function to level out that response (which is the average of on-, off- and very-off-axis responses), and then attenuated the 6.3kHz peak a touch more.
There's a hint of some HF diffraction issues, which will probably be the grille attachments right at the horn exit. I'm hopeful that some dense foam just inside the grille might help there.
Next up, BR ports:
Midrange leakage looks okay to me. Hornresp was a bit of a way out in its predictions of the port resonances, but there's a very irregular interior which might be helping to break things up a little.
And confirmation of tuning, close-micing one of the drivers:
The settings went in on the DCX2496 that now handles the easy stuff - summing to mono for subwoofer outs, stuff like that. Most of the EQ is done in the NU3000DSP amps.
Finally, I remembered to include phase on this one:
It goes round a couple of times, but its a pretty smooth phase response.
I'm really pleased with how these sound having dialled the EQ in. Now all that's left to do is decide between weighting for a B&K curve, or leave it ~flat.
Out of curiosity, I put a meter across a bit of wire connected to one of the terminals. The 10"s in parallel come in at around 3ohm, so I think an NU6000 may have been unsuitable here.
That's all for now, I'm gonna listen some more.
Chris
The initial graphs were okay, but it turned out I'd done a brain fart and delayed the tweeter instead of the 10"s, giving a weird dip/peak around 900-1kHz and lots of exciting phase angles.
Corrected that, and re-addressed the relative SPLs of the woofers and tweeters, and got the following:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Then, with a bit of averaging and smoothing:
An externally hosted image should be here but it was not working when we last tested it.
Not bad!
I ran the Auto-EQ function to level out that response (which is the average of on-, off- and very-off-axis responses), and then attenuated the 6.3kHz peak a touch more.
There's a hint of some HF diffraction issues, which will probably be the grille attachments right at the horn exit. I'm hopeful that some dense foam just inside the grille might help there.
Next up, BR ports:
An externally hosted image should be here but it was not working when we last tested it.
Midrange leakage looks okay to me. Hornresp was a bit of a way out in its predictions of the port resonances, but there's a very irregular interior which might be helping to break things up a little.
And confirmation of tuning, close-micing one of the drivers:
An externally hosted image should be here but it was not working when we last tested it.
The settings went in on the DCX2496 that now handles the easy stuff - summing to mono for subwoofer outs, stuff like that. Most of the EQ is done in the NU3000DSP amps.
Finally, I remembered to include phase on this one:
An externally hosted image should be here but it was not working when we last tested it.
It goes round a couple of times, but its a pretty smooth phase response.
I'm really pleased with how these sound having dialled the EQ in. Now all that's left to do is decide between weighting for a B&K curve, or leave it ~flat.
Out of curiosity, I put a meter across a bit of wire connected to one of the terminals. The 10"s in parallel come in at around 3ohm, so I think an NU6000 may have been unsuitable here.
That's all for now, I'm gonna listen some more.
Chris
I try to take care of them when moving them around, but probably not. In 6 months, though, I might've plucked up the courage to try a synergy-style build
Cheers JMF!
Chris
Big gig coming up tomorrow - new tops, 4x subs, plus a pair of wedges.
I've spent a little while setting the limiters and choosing the LF cutoff for the subs by playing a variety of music, with the amps turned up but speakers disconnected. 35Hz seemed to be a good compromise - reaching for 30Hz needed even more boost, but stopping at 40Hz meant the midbass amp was often clipping first. I'd much rather the subs limit first, since compression there will sound much more benign than the mids, but I'll still know I'm running close to the edge.
Because of the fairly shallow rolloff, -10dB is in the mid-20s. Should be impressive.
That might all change, of course, in a different room or outdoors.
Chris
I've spent a little while setting the limiters and choosing the LF cutoff for the subs by playing a variety of music, with the amps turned up but speakers disconnected. 35Hz seemed to be a good compromise - reaching for 30Hz needed even more boost, but stopping at 40Hz meant the midbass amp was often clipping first. I'd much rather the subs limit first, since compression there will sound much more benign than the mids, but I'll still know I'm running close to the edge.
Because of the fairly shallow rolloff, -10dB is in the mid-20s. Should be impressive.
That might all change, of course, in a different room or outdoors.
Chris
Gig went rather well. Ran a bit late, but I was expected to set up a PA system, monitors, the lot, in an unknown venue, in 30 mins. Venue size was 40-50 people seated. Not tiny, but not huge.
To give you an idea, the stage was about as wide as the four subs. Fire escape to one side, toilets to the other. The main speakers were up against the walls at each side, 4 subs across the front of the stage. Wedges and amps behind each main speaker.
Music was mostly folky, from gentle harmonies w/guitar to some more stompy, upbeat stuff.
The subs did very well (once I dialed the level in) - there was a lovely visceral feeling to the low end, even at fairly modest volumes. I suspect that's down to the low-frequency extension.
I wasn't quite happy with the tops at times - they came across a bit bright. They were toed in around 30 degrees, to try to cut down on near reflections (difficult, since they were almost touching the walls). I think I might dial down the top end a touch next time. The bands were rehearsing in the room when I'd got everything up and running, so I didn't have much chance to play around.
All that said, headroom was abundant - no sign of anything struggling at all. I had a couple of band members come and tell me that the speakers sounded very good, which was a proud moment for me.
That's all for now. Took a couple of photos that I'll post up soon.
Chris
To give you an idea, the stage was about as wide as the four subs. Fire escape to one side, toilets to the other. The main speakers were up against the walls at each side, 4 subs across the front of the stage. Wedges and amps behind each main speaker.
Music was mostly folky, from gentle harmonies w/guitar to some more stompy, upbeat stuff.
The subs did very well (once I dialed the level in) - there was a lovely visceral feeling to the low end, even at fairly modest volumes. I suspect that's down to the low-frequency extension.
I wasn't quite happy with the tops at times - they came across a bit bright. They were toed in around 30 degrees, to try to cut down on near reflections (difficult, since they were almost touching the walls). I think I might dial down the top end a touch next time. The bands were rehearsing in the room when I'd got everything up and running, so I didn't have much chance to play around.
All that said, headroom was abundant - no sign of anything struggling at all. I had a couple of band members come and tell me that the speakers sounded very good, which was a proud moment for me.
That's all for now. Took a couple of photos that I'll post up soon.
Chris
So, the reason they were coming across a bit bright was that I had averaged on-, nearly-on-, and off-axis responses. The drooping top end of the off-axis response meant that the rising top-end of the on-axis responses was averaged out pretty flat. Off-axis is a bit dull, and on-axis is overly bright.
I'm going to go back to basics this time around, and measure HF and MF seperately at lots of angles to see where the off-axis response becomes, shall we say, less useful.
There'll be lots of data to process after that - always fun.
Chris
I'm going to go back to basics this time around, and measure HF and MF seperately at lots of angles to see where the off-axis response becomes, shall we say, less useful.
There'll be lots of data to process after that - always fun.
Chris
So, they sound different again.
Took a lot of measurements, then did an average (weighted towards on-axis this time!) of each of HF and MF. The mids showed a consistent dip at 900Hz, so I went for a 750Hz crossover. LR4.
Played with time alignment a little, and got this:
The reverse-phase dip is pretty good. Not quite symmetrical, but not far off.
There's also a measurement of the nearfield bass response, taken by one of the side handles. Moving the mic seems to have affected the measurement, so I assume the rough bottom end measured has been down to reflections from buildings etc.
After all the measurements and EQing each driver, I added a couple of tweaks, knocking down a narrow-ish on-axis peak at 6.3kHz, and adding some sparkle up at 14kHz. REW refuses to auto-EQ past 10kHz, and the ECM8000 mic isn't reliable up there anyway. I played with manual EQs for a while to get the response flat on-screen, and then played with the boost by ear.
I'm very very pleased with how these sound now.
Chris
Took a lot of measurements, then did an average (weighted towards on-axis this time!) of each of HF and MF. The mids showed a consistent dip at 900Hz, so I went for a 750Hz crossover. LR4.
Played with time alignment a little, and got this:
The reverse-phase dip is pretty good. Not quite symmetrical, but not far off.
There's also a measurement of the nearfield bass response, taken by one of the side handles. Moving the mic seems to have affected the measurement, so I assume the rough bottom end measured has been down to reflections from buildings etc.
After all the measurements and EQing each driver, I added a couple of tweaks, knocking down a narrow-ish on-axis peak at 6.3kHz, and adding some sparkle up at 14kHz. REW refuses to auto-EQ past 10kHz, and the ECM8000 mic isn't reliable up there anyway. I played with manual EQs for a while to get the response flat on-screen, and then played with the boost by ear.
I'm very very pleased with how these sound now.
Chris
Next steps...
So, for now there's not a whole lot to do. I'd like to get the P-Audio 21" driver up and running, but I'm still moving everything in a small hatchback with the back seats folded down. Until I sort something bigger, the 4x subs, 2x tops, 2x 12" coaxial monitors, plus amps etc is about all I can fit.
When I do have something bigger, I think I might go ported or TH for the 15"s, which would mean more headroom at the bottom end.
Not entirely sure if that's necessary, though: a pair of the current 15" subs will match a single 2x10" top for SPL down to 45Hz, -10dB around 30Hz.
Do I need any more bass than that? - Reading around here and also at some install systems I've worked with, it seems that having mid-highs with up to 10dB of extra output ability over the subs is the way to go.
Think I need to do some more gigs with this setup and see what gives up first.
Chris
PS - couple of pictures. I know you all like pictures.
So, for now there's not a whole lot to do. I'd like to get the P-Audio 21" driver up and running, but I'm still moving everything in a small hatchback with the back seats folded down. Until I sort something bigger, the 4x subs, 2x tops, 2x 12" coaxial monitors, plus amps etc is about all I can fit.
When I do have something bigger, I think I might go ported or TH for the 15"s, which would mean more headroom at the bottom end.
Not entirely sure if that's necessary, though: a pair of the current 15" subs will match a single 2x10" top for SPL down to 45Hz, -10dB around 30Hz.
Do I need any more bass than that? - Reading around here and also at some install systems I've worked with, it seems that having mid-highs with up to 10dB of extra output ability over the subs is the way to go.
Think I need to do some more gigs with this setup and see what gives up first.
Chris
PS - couple of pictures. I know you all like pictures.
Some more pictures, managed to get the 21" driver up and running.
http://www.diyaudio.com/forums/subwoofers/282672-something-big-p-audio-sd21-1800n-4.html#post4737807
Enjoyed the gig, but even with all that cone area, the subs were still the weak link.
I've another outdoor gig coming this weekend. Might use the 21", might not. For now, I'm going to play around with Hornresp and see what I can get out of some ported 15"s - while its nice to be able to get any LF cutoff you like with the sealed cabinets, its not especially useful when its just not loud enough. 40Hz and loud would be better than 30Hz and clipping everything.
Chris
http://www.diyaudio.com/forums/subwoofers/282672-something-big-p-audio-sd21-1800n-4.html#post4737807
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Enjoyed the gig, but even with all that cone area, the subs were still the weak link.
I've another outdoor gig coming this weekend. Might use the 21", might not. For now, I'm going to play around with Hornresp and see what I can get out of some ported 15"s - while its nice to be able to get any LF cutoff you like with the sealed cabinets, its not especially useful when its just not loud enough. 40Hz and loud would be better than 30Hz and clipping everything.
Chris
Another weekend, another gig. This one was a similar sort of setup to the previous: 2x 2x10" tops, 4x 1x15" & 1x 1x21" subs.
I suspect I'd have more output if I put the subs on the ground, but rain was forecast (and arrived), so I wanted to make sure it'd be easy to pull everything further under cover.
This time, I hit clipping on the mids once or twice. Wasn't audible, though - probably a testament to bi-amping. I don't know how the subs fared, though. I haven't got the limiting set up correctly yet, and only realised this after the first set.
The 21" sub is a real pain to move around, so I'm playing with sims of the 15"s in ported configurations, maybe something like Art's 2x15" PPSL, though I quite like having four seperate cabs. That'll be a little way down the line. Next month is a 3-day city-wide festival, and the venue booked me back in February. Looks like I'm doing something right.
Couple more pictures from another gig. This one was quite asymmetrical, but nobody minded much. The room was rather small, with maybe 50 people in front of the speakers. Way too much kit for that room, but I wasn't told room dimensions, and could only find pictures of the outside, which looked like an old barn. I don't think the amps went above -12dB all night.
... and one more from the gig in a previous post.
That's all for now
Chris
An externally hosted image should be here but it was not working when we last tested it.
I suspect I'd have more output if I put the subs on the ground, but rain was forecast (and arrived), so I wanted to make sure it'd be easy to pull everything further under cover.
This time, I hit clipping on the mids once or twice. Wasn't audible, though - probably a testament to bi-amping. I don't know how the subs fared, though. I haven't got the limiting set up correctly yet, and only realised this after the first set.
The 21" sub is a real pain to move around, so I'm playing with sims of the 15"s in ported configurations, maybe something like Art's 2x15" PPSL, though I quite like having four seperate cabs. That'll be a little way down the line. Next month is a 3-day city-wide festival, and the venue booked me back in February. Looks like I'm doing something right.
Couple more pictures from another gig. This one was quite asymmetrical, but nobody minded much. The room was rather small, with maybe 50 people in front of the speakers. Way too much kit for that room, but I wasn't told room dimensions, and could only find pictures of the outside, which looked like an old barn. I don't think the amps went above -12dB all night.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
... and one more from the gig in a previous post.
An externally hosted image should be here but it was not working when we last tested it.
That's all for now
Chris
Hi Joh,
Thanks for the encouragement.
I find it helps, actually writing everything down as well - it makes sure I'm being coherent, and if I have any good ideas, I can come back to them later.
I recently got myself an SPL meter, so I can get an idea of how I'm doing. Some commercial cabinets seem to exagerrate their specs, though. A 1x12" box on a stick doing >130dB? Seems unlikely.
Chris
PS - there's something very small in the pipeline, might be interesting.
Thanks for the encouragement.
I find it helps, actually writing everything down as well - it makes sure I'm being coherent, and if I have any good ideas, I can come back to them later.
I recently got myself an SPL meter, so I can get an idea of how I'm doing. Some commercial cabinets seem to exagerrate their specs, though. A 1x12" box on a stick doing >130dB? Seems unlikely.
Chris
PS - there's something very small in the pipeline, might be interesting.
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