ShinOBIWAN said:
Tell me about it. I recently picked up Metal-licker's new album "Death Magnetic". What I didn't realise is that "Death" means what's happened to the dynamic range. Oh yeah, and the distortion is off the scale. Anyone wanting to enjoy the album should get hold of the version ripped from that game designed for people who'd rather press buttons than play a real guitar.
ShinOBIWAN said:
Yeah, that's what I did with mine (wrapped it all in some wadding/batting/whatever the haberdashery dwelling grannies call it).
Still waiting on side cabinets not much I can do about that but, in the meantime, decided to tackle something else that annoys me; cabling.
Active loudspeaker setups require more cables and so can cause confusion when hooking up and fooling around. My current set of cheap proel cables are fine but they're too short for the new install so it was a choice of buy or build.
Pro audio cables aren't expensive because there's virtually none of the BS that surround home audio cables but I still like to DIY these small items even if the cost savings aren't large.
These are the new balanced patch cables that sit between the DACs and amps. I colour coded them for easier identification too. Nothing exotic just neutrik connectors with van damme balanced patch cable.
Its a small DIY but worth it IMO.
Active loudspeaker setups require more cables and so can cause confusion when hooking up and fooling around. My current set of cheap proel cables are fine but they're too short for the new install so it was a choice of buy or build.
Pro audio cables aren't expensive because there's virtually none of the BS that surround home audio cables but I still like to DIY these small items even if the cost savings aren't large.
These are the new balanced patch cables that sit between the DACs and amps. I colour coded them for easier identification too. Nothing exotic just neutrik connectors with van damme balanced patch cable.
Its a small DIY but worth it IMO.
It does but don't I use the splitter cable that was provided. Instead I've got a snake distribution box where all 16 ins and 16 outs can be easily label and accessed. From the snake I use patch cables to whatever equipment is needed.
EDIT:
Its similar to one of these:
http://www.thomann.de/gb/the_sssnake_sk415-30_multicore.htm
EDIT:
Its similar to one of these:
http://www.thomann.de/gb/the_sssnake_sk415-30_multicore.htm
Hey guys,
Finally tested the room out and have a problem. The treatments are effective above around 200hz and somewhat effective to 100hz but below 100hz they do virtually nothing and this where I have a strong issue.
Allow me to show a before and after snap shot at the listening position of the right speaker only then I'll explain the problem:
Before treatment
After treatment
As can be seen, there's a very nice improvement in overall damping of the upper bass and higher frequencies but after running sine waves and listening to music there's something weird going on at around 50-90hz and its at its worst around 70hz. The bass at the listening position is very strong and strangely appears not to come from the speaker but from the rear and left side of the room as opposed to the front right where the speaker is located. Also just turning your head from looking straight forward to looking 90degrees right makes the bass completely disappear! But move your head straight or to the left and it comes back.
After a process of elimination and measurements I've narrowed down possible candidates to the cause. Before treating the room there was no cabinet at the front and between the speakers so no problem at 70hz back then. I dropped the cabinet face down onto the floor then ran a tone generator with sines through the right speaker as before and the weird phasey boom around 70hz disappeared. The exact cause is the cabinet creates two small alcoves that the speakers partially sit within and this appears to be where the problem is created.
For now I've come up with a bandaid just to make the system listenable, actually its much better but I'm still aware of a problem in the bass. What I've done is put a high Q and deep notch filter in at 70hz along with digital room correction. Oddly despite the deep notch showing as a severe drop in the frequency response its not that noticeable because its filled in by the resonance. Hardly fidelity though since your listening to controlled boom at 70hz.
Here's some possible solutions I've come up with:
- The problem will be smoothed once the left channel is playing thus placing another low frequency source within the room. Usually such a move would smooth bass problems. But I'm not at all confident this will be true since the left channel is in a mirror image situation with the right so it makes sense that the same problems will be present.
- I was wondering about membrane traps located in the alcoves where the loudspeaker sit? Each alcove could accommodate 1x 60cm x 170cm panel and 2x 40cm x 170cm panels. All with a max total depth of 4". Can these be tuned low enough to affect 50-100hz with the concentration around 70hz?
- What about multiple small subs? I could very easily and quickly build 3 small sealed cubes based around the unused Peerless XLS10 drivers I have already. I've read the Harman paper about multiple subs for smoothing room response and one at the mid point for side walls and rear wall looks promising. These would work from around 80-90hz.
Any thoughts on these idea's?
I like the idea of trying the membranes around the speakers first 'cause its cheap and no problems building them.
Finally tested the room out and have a problem. The treatments are effective above around 200hz and somewhat effective to 100hz but below 100hz they do virtually nothing and this where I have a strong issue.
Allow me to show a before and after snap shot at the listening position of the right speaker only then I'll explain the problem:
Before treatment
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.
After treatment
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.
As can be seen, there's a very nice improvement in overall damping of the upper bass and higher frequencies but after running sine waves and listening to music there's something weird going on at around 50-90hz and its at its worst around 70hz. The bass at the listening position is very strong and strangely appears not to come from the speaker but from the rear and left side of the room as opposed to the front right where the speaker is located. Also just turning your head from looking straight forward to looking 90degrees right makes the bass completely disappear! But move your head straight or to the left and it comes back.
After a process of elimination and measurements I've narrowed down possible candidates to the cause. Before treating the room there was no cabinet at the front and between the speakers so no problem at 70hz back then. I dropped the cabinet face down onto the floor then ran a tone generator with sines through the right speaker as before and the weird phasey boom around 70hz disappeared. The exact cause is the cabinet creates two small alcoves that the speakers partially sit within and this appears to be where the problem is created.
For now I've come up with a bandaid just to make the system listenable, actually its much better but I'm still aware of a problem in the bass. What I've done is put a high Q and deep notch filter in at 70hz along with digital room correction. Oddly despite the deep notch showing as a severe drop in the frequency response its not that noticeable because its filled in by the resonance. Hardly fidelity though since your listening to controlled boom at 70hz.
Here's some possible solutions I've come up with:
- The problem will be smoothed once the left channel is playing thus placing another low frequency source within the room. Usually such a move would smooth bass problems. But I'm not at all confident this will be true since the left channel is in a mirror image situation with the right so it makes sense that the same problems will be present.
- I was wondering about membrane traps located in the alcoves where the loudspeaker sit? Each alcove could accommodate 1x 60cm x 170cm panel and 2x 40cm x 170cm panels. All with a max total depth of 4". Can these be tuned low enough to affect 50-100hz with the concentration around 70hz?
- What about multiple small subs? I could very easily and quickly build 3 small sealed cubes based around the unused Peerless XLS10 drivers I have already. I've read the Harman paper about multiple subs for smoothing room response and one at the mid point for side walls and rear wall looks promising. These would work from around 80-90hz.
Any thoughts on these idea's?
I like the idea of trying the membranes around the speakers first 'cause its cheap and no problems building them.
I think I might be talking to Granny about baking apple pies, but that big cabinet isn't the problem, is it? You could store a lot of energy in there and the doors are suspended and can't be thought of as rigid. Is it empty? Might it be acting as a trap or a resonator? Either way, modal distribution would be affected.
Hi Ant,
You really need deep corner traps to seriously affect low bass tones - the edges of my corner traps are about 60cm from the room corners, and I don't think they will do much at 70Hz.
The guy at RealTraps advised me to always test with both speakers in use, as that's the real scenario.
You could try a Helmholtz resonator, tuned to the problem frequency, but obviously the best solution would be sorting the cabinet, if that's what's caused the problem.
You really need deep corner traps to seriously affect low bass tones - the edges of my corner traps are about 60cm from the room corners, and I don't think they will do much at 70Hz.
The guy at RealTraps advised me to always test with both speakers in use, as that's the real scenario.
You could try a Helmholtz resonator, tuned to the problem frequency, but obviously the best solution would be sorting the cabinet, if that's what's caused the problem.
Hey Gordon.
I'd forgot about this thread for awhile so apologies on the late reply.
Good advice, the effect is limited to the left channel and the right isn't as bad. Asymmetrical room is the cause. With both playing the problem is lessened. It could still do with some looking at though and I think I might build 3 compact subs to place at the mid points along the side and rear walls. Geddes' multisub approach appears to be getting a lot of attention and some good reviews so that's the one I'll likely pursue.
I still have a couple of those XLS10 that the pair of us bought so it won't cost much other than MDF.
I had the same recommendation from someone else who's opinion I trust. He also outlined some construction details for a membrane trap tuned to about 80hz and effective for about a half to three quarters of an octave either side. Its this that I'll likely go with. The construction is simple and they appear to quite effective when placed in corners behind the loudspeakers.
I'd forgot about this thread for awhile so apologies on the late reply.
Good advice, the effect is limited to the left channel and the right isn't as bad. Asymmetrical room is the cause. With both playing the problem is lessened. It could still do with some looking at though and I think I might build 3 compact subs to place at the mid points along the side and rear walls. Geddes' multisub approach appears to be getting a lot of attention and some good reviews so that's the one I'll likely pursue.
I still have a couple of those XLS10 that the pair of us bought so it won't cost much other than MDF.
I had the same recommendation from someone else who's opinion I trust. He also outlined some construction details for a membrane trap tuned to about 80hz and effective for about a half to three quarters of an octave either side. Its this that I'll likely go with. The construction is simple and they appear to quite effective when placed in corners behind the loudspeakers.
And finally the side cabinets appear! They made me wait weeks for these after that cockup I mentioned earlier in the thread but good things do come to those who wait.
An externally hosted image should be here but it was not working when we last tested it.
ShinOBIWAN said:
Ah, yeah. Still got two of those in my loft!
The other two are being used in a single sealed box as a push-push sub, being driven from an Alesis power amp. It makes a nice sub for music and movie duties, though my eventual plan is to use the other two to end up with a pair of twin subs... when I get time.
Good luck on the membrane trap - would like to see pics as always.
ShinOBIWAN said:
That looks superb! Though... erm... you're not gonna get much sparkle from the speaker on the left.
sploo said:
In the loft?! Did they misbehave or something? Seems a bit harsh this time of year, put a warm blanket over them.
Thanks. Will see what happens with those. Apparently they can be little tricky to tune so expect I'll miss the mark on the first attempt. Construction is very simple though.
New surround speakers in the form of Genelec 8020A.
These are small active speakers with 3/4" tweeter in a waveguide and 4" mid bass. The amplification is a whole 20w of sheer power per driver. Impressively the cabinet is made out of extruded Aluminium. I did the knuckle test and I'd say they're as good or maybe even slightly better than the LGT speakers I did.
The don't get particularly loud but this isn't a big problem for surrounds. I took a listen today with them setup as mains and I have to say I was surprised. They manage a reasonable impression of a moderately sized speaker despite their size and extension is useful to about what seems like 50hz. Imaging and stage were both great too considering the price. A smooth and well balanced sound was my thought.
Here's a couple of shots to show just how small these things are. I'm amazed they managed to fit in 2 amps, PSU, an active crossover and overload circuitry into such a tiny space and get it to sound good too.
These are small active speakers with 3/4" tweeter in a waveguide and 4" mid bass. The amplification is a whole 20w of sheer power per driver.
Impressively the cabinet is made out of extruded Aluminium. I did the knuckle test and I'd say they're as good or maybe even slightly better than the LGT speakers I did.The don't get particularly loud but this isn't a big problem for surrounds. I took a listen today with them setup as mains and I have to say I was surprised. They manage a reasonable impression of a moderately sized speaker despite their size and extension is useful to about what seems like 50hz. Imaging and stage were both great too considering the price. A smooth and well balanced sound was my thought.
Here's a couple of shots to show just how small these things are. I'm amazed they managed to fit in 2 amps, PSU, an active crossover and overload circuitry into such a tiny space and get it to sound good too.
gainphile said:
I've done more investigating since posting about it on here and the dip is caused by the distance from front wall to baffle. Its likely that things would be improved with dipole subs.
I also did a little reading and found recommendations for what this distance should ideally be. Below 20cm is OK providing the speaker is quite directional in the mid frequencies. Between 20cm and 1.1m is not recommended because this places the dip in the band above 90hz where it can't be influence and lessened by a separate sub which relies on the range below this to ensure non directional frequencies. Anything above 1.1m is fine and the further away the lower in frequency the dip moves.
I'm in an awkward position because the cabinet depth makes it impossible to get under 20cm from baffle to wall so I've gone with getting the distance to 1.2m and plan to make an attempt to correct with membrane bass traps behind and around the speakers. If the result isn't satisfactory I'll go with a more brute force approach by introduce at least 2, possibly 3, compact subwoofers.
ShinOBIWAN said:In the loft?! Did they misbehave or something? Seems a bit harsh this time of year, put a warm blanket over them.
Yeah, they've been bad, and have been sent to the naughty step.
They will get used, if and when I can ever get this spherical speaker cabinet idea working right. I've just poured several cups of expanding polyurethane foam into a mold in the airing cupboard (as it was the only place warm enough for the mixture to activate). The things we speaker builders do eh...
Good luck with the bass traps - looking forward to seeing more photos as always.
ShinOBIWAN said:Sounds interesting, look forward to seeing and hearing how that turns out. One things for certain, you'll have no problems with joints expanding on that!
It turned out sort of like an amorphous blob.
I'm trying to make an internal mold of a spherical enclosure (turned from layers of MDF). My idea is to make an external mold for the outside of the speaker, then suspend a sacrificial lump inside (molded from the inside of the original), around which will be pored the casting material - probably concrete.
Once cured, the finished enclosure would be removed from the external mold, and the internal mold (current experiments are using poly foam) would be mechanically removed.
Despite doing all the calculations on expansion, adding bit more, and getting the temperature right, it didn't expand anywhere near as much as the datasheet claimed. I'm casting it inside a bag (so it doesn't stick) but this means it really needs to build up some pressure to be accurate. Not worked this time, maybe I'll try again with a larger amount of the foam.
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