That’s really quite good, but seriously what are the woofers doing? I'd expect at least a 3-6 dB boost when they were engaged.
Room Acoustics, minimal treatment and measurements
Afternoon all. Thought this might be helpful to some with wondering if room treatments can help with your 2-channel, and how to help visualize and measure what you may not fully grasp hearing wise. I am just using a Mac Laptop and cheapo microphone, and REW, and 6 insulation panels.
This is my Step Fathers system, and pretty much empty LARGE basement listening space. There is a LOT of echo-reverb-ringing that (to my ears) over excites mid to upper frequencies, like being in a busy store/restaurant. With music, this can in ways help make a recording sound like it's in a larger studio/hall/space, but it also mashes a lot together and can over-color the music. This results in lost focus and change in ACTUAL recorded acoustics: so an intimately microphoned musician will sound like an empty room, where an empty room sounds like an empty gymnasium. This, also over-washes a bit of the mid-range and higher bass-losing it's tone and timbre. Major thanks to @erik_squires who has been gracious to help with this process with dead-on advice.
FULL BASEMENT MEASUREMENTS:
34'long x 22'wide x 10'high
LISTENING AREA MEASUREMENTS:
15'long x 22'wide x10'high
Empty room, no treatments and RT60 plot. Listening seat is *in the middle of the whole basement space, under an 18" boxed beam.*
"Treated" room, with RT60 plot. Notice the overall mid-upper frequency taming from 700ms of "ring/decay", to 500ms. Even with this, if you snap your fingers, you still hear a flutter echo. This is from the whole other half of the basement room behind me, mostly.
Crude room response measurement:
Sketch and measurements of where things are in the listening room:
I hope this is helpful and gives you some things to try out that don't cause major disruptions to your system, until you really determine if and where your issues are and then you can buy and mount things. My next step is to see where ON the walls I can place absorbing panels, and how many might be needed for a nominal improvement. My thinking is the bigger issues are the ceiling, front wall, and then 'filling' the space behind the seat just to eat up ambient stray ringing.
Showing 11 responses by erik_squires
If there is no bass to mid-bass crossover, then I expect destructive interference (frequency dips) somewhere, either horizontally or vertically. I also expect the 7" drivers would sound much better if not trying to reproduce 20 Hz. It may be worthwhile talking to Legacy and asking if the woofers actually have a low pass filter. Your measurements, and the impedance charts from Poland suggest the answer is no. The way to tell without opening your speakers is with an impedance sweep. REW has a way to do this if you make a custom jig, or you can purchase Dayton DATS. Measure the combined impedance, and separately. Take a look at this blog post to understand "High pass impedance" and "Low Pass Impedance"
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If this was my system, I'd bi-amp, using a miniDSP as an active crossover in front of the amps. It sounds really good. This is going to give you the ability to properly high pass the mid-woofers, low pass the woofers, which will improve off-axis imaging and overall smoothness, give you a lot of extra headroom AND let you equalize the 12" drivers to function as subs. Also, I'd plug the ports, which will raise the -3 dB a little, but also slow down the rolloff below 100 Hz significantly. Fortunately, plugging the ports just takes a pair of clean socks. I suggest organic cotton ... :D Really anything that closes the ports and doesn't get lost. You may seriously want to try plugging the ports and re-measuring anyway. You may find this extends the bass in just the right way. |
I was wrong btw, I found I think a polish sight that says the min impedance is 4 Ohms, but still, with bi-amping you can set levels independently. The site also noted poor off-axis integration, a potential sign of the effects of the overlapping woofer/mid-woofs, so I really think at the very least, bi-amped with an EQ in front of the woofer amps is going to give you everything you need. |
Normally, I say to leave a speaker be and not to try to hack it very much. Either love it as is or get something else. In this case though I feel you have a number of approaches which could be really worthwhile for you and your dad. Compared to a traditional multi-way speaker, the Legacy focus seems to be "missing" the crossover between the 7" and woofers. While we can argue about the end result, two things are happening: The lack of a crossover = 2 Ohm minimum load, and there's some interference between the woofer and mid-woofs(7"). Based on that, I think in the future there are a number of ways to deal with it which improve the bass performance significantly: I. Passive bi-amping. The reason this is an excellent idea here is that the lack of a crossover means you have a very low minimum impedance in the bass range. Less capable amps can handle just the bass or the mid-treble section but not both. Separate the two sections and each has ~ 4 Ohms minimum. II. Active bi-amping. Put a miniDSP in front of your two amplifiers. This will give you excellent EQ capabilities, and you’ll be able to add the "missing" filters. Again, you end up with 2 x 4 Ohm sections instead of one 2 Ohm section. III. Low impedance capable amp, like a stiff Krell or Sanders or Coda. Something that will handle the 2 Ohm or lower load in the bass section. |
I found the Stereophile measurements for the predecessor. If the two units are similar, then your measurements are actually quite normal for the line. The review also goes into some details about the unique crossover choices, which your measurements kind of confirm. There’s a lot here that goes against the grain for most loudspeakers, including the unusually high -3 dB point given the size of the woofers. I suggest moving them back towards the wall, and consider re-testing after plugging the ports. You may find the slower rolloff preferable. Worth listening to it. So, all my advice about sound absorption was correct, you could even do a little more, but if it were me, I’d want more bass than you have so far.
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OP: Maaaaaybe? It could be as simple as your speaker cables are not hooked up right at the amp or that the ends of the bi-wire cable are swapped somewhere. That's the bi-wiring aspect of this complicates things. It's worth getting some plain zip cord and trying the speaker out with the original straps on. Another test you can do is to play just 1 speaker at a time. This eliminates the possibility of left/right cancellation. If you still have that 24 db/octave drop off then its in the speaker.
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SO, yes, straps and cables are fine, but you can do some more basic tests first. Since you are bi-wiring it’s quite possible your problem is one speaker or woofer section is wired out of phase with the other. Check for that before attaching straps. That would explain the lack of bass and lack of room mode problems. Some basic tests with a multimeter include making sure that the two paris of terminals at the end of the biwiring have perfect continuity (disconnect the amp first!) and that the woofer sections show around 3-16 Ohms. Not sure what it should be honestly, varies by speaker. A 1.5 to 9V battery and wires can be used to test the woofer sections. Attaching + to + and - to - should have the woofers moving in the same direction, usually towards the listener. 9V is about 10 watts if the battery could actually deliver that much current (it can’t), so it’s generally safe. The battery voltage will sag long before you get to 10W. All 4 woofers should move in the same direction when tested this way. |
OP: First, you are going to be very glad of the treatment, but now that I see the measurements and the specs, I think your woofers are not working at all. You may be missing the straps that connect the woofer to the 7" drivers. Based on specs, the 7" are crossed at 120 Hz, which is exactly what we are seeing here. Play loud music and go touch the woofers.
Erik |
