Curious if anyone here has threaded the needle with this. Use these drivers for example...
2: 8 ohm, 86 dB efficient woofers wired in parallel (should make them 92 dB).
1: 8 ohm midrange, 87 dB
Essentially in this configuration there would be 92 dB of efficiency from the combined woofers, paired with 87 dB efficient midrange.
Seems like this would be a bass heavy mess until baffle step loss is considered. I know how baffle step loss works, it's generally 6 dB, but that's not static, it starts at roughly 1khz and ends up 6 dB down near roughly 80 Hz.
My question is... Once baffle step loss is considered, do you guys think that 87 dB mid will work with the 92 dB woofer configuration, crossed at 350 to 400 Hz?
Also pertinent... Lets assume we won't do a 3.5 way xover, keep it a 3 way to get an easier answer.
2: 8 ohm, 86 dB efficient woofers wired in parallel (should make them 92 dB).
1: 8 ohm midrange, 87 dB
Essentially in this configuration there would be 92 dB of efficiency from the combined woofers, paired with 87 dB efficient midrange.
Seems like this would be a bass heavy mess until baffle step loss is considered. I know how baffle step loss works, it's generally 6 dB, but that's not static, it starts at roughly 1khz and ends up 6 dB down near roughly 80 Hz.
My question is... Once baffle step loss is considered, do you guys think that 87 dB mid will work with the 92 dB woofer configuration, crossed at 350 to 400 Hz?
Also pertinent... Lets assume we won't do a 3.5 way xover, keep it a 3 way to get an easier answer.
Also important in this equation... Assume the efficiency ratings for all drivers are accurate, and rated at 2.83v.
There's baffle step and there's room gain. In free 4π space, you'd be quite allright, more so because a slightly dropping power and level curve seems to be preferable. Room gain can and will bring you trouble (below 200Hz) and can easily be +9dB, but fluctuating like h#$@ll, because of room modes.
Another option would be driving the woofers in series. That would bring you +0dB, an easy load on the amplifier and the opportunity to pad the mid down a bit with a resistor that also could bring back-EMF distortions down a bit, if those would be present in the preferred midrange.
I hope you calculated the efficiency/sensitivity from the TSP and not from the data sheet by the way. The last method brings you off quite a bit.
Another option would be driving the woofers in series. That would bring you +0dB, an easy load on the amplifier and the opportunity to pad the mid down a bit with a resistor that also could bring back-EMF distortions down a bit, if those would be present in the preferred midrange.
I hope you calculated the efficiency/sensitivity from the TSP and not from the data sheet by the way. The last method brings you off quite a bit.
Why? If BS is related to baffle (and all the perimeter) and the wavelengths are 0,3 m for 1kHz well, now there is the directivity index that takes place!
80 Hz lambda/2 is ~3 m
Hmmm
Serious problem!
But, hey, the problem is the nature of sound: the box is little compared to long waves and those approaching the size of the box experience ghost replicas, but nevertheless sound arrives to you, so somehow all the equations bring to same solution.
Fantastic response, I wasn't even considering room gain. And that's a tough one to account for because every room is a little different.
I haven't actually measured the drivers yet, but the woofers are Scanspeak and the mid is Satori and I've found those to be pretty spot on.
I'm tempted to try this. In the past I've always tried to get fairly close in efficiency between a mid and a woofer, but I still end up padding the midrange quite a bit. One that comes to mind is a TMWW I did using a pair of 8" (wired in parallel) woofers that were 85 dB with a 91 dB 7" Wavecor for the midrange. Obviously the efficiency gap on that build was tighter (92 dB woofers vs 91 dB mid), but I still had to pad that mid quite a bit. I did do a 3.5 way xover with that one. I'm not opposed to doing a 3.5 way on this one, but ultimately wanted to know what the biggest swing in driver efficiency people have used (midrange vs woofer).
I'm asking because I was hoping to avoid building a test cabinet. I do have 2 of the 8 ohm mids and could just do a MTMWW, but was also hoping to keep it a TMWW. Guess I should just build a test cabinet and give this a whirl.
Not sure why I can't quote your response? But @picowallspeaker I'm not sure what you're actually debating with this statement...
While the amplifier can easily handle the 4 ohm load, wiring the woofers in series is definitely an option. But the speakers would then be 96 dB efficient, and 8 ohm which would diminish amplifier headroom. But they're Hypex NCx500 amps so there's plenty of power. IMO, this is another good topic as well (4 vs 8 ohm drivers> amp power> does more headroom, or an easier impedance sound better on larger floor-standers?).
In my experience, the bass response and lower midrange response of a speaker sounds best, most correct, if the design has a flat response in 4pi space (anechoic), even though that will result in a non-flat result in a real room.
A speaker which is flat from 40 Hz to 400 Hz anechoic will sound correct when placed in a real room. Of course the speakers and listener will need to be positioned properly to get the best result. Some people find room correction software such as REW and Dirac to be helpful if ideal placement is not possible or if the room has some bad modes. But this process presumes that the speaker was designed correctly.
I understand that some people will disagree with me on this.
To your original question, I think that a pair of 86 dB sensitivity woofers, in parallel, would mate up nicely with a 87 dB sensitivity midrange.
j.
A speaker which is flat from 40 Hz to 400 Hz anechoic will sound correct when placed in a real room. Of course the speakers and listener will need to be positioned properly to get the best result. Some people find room correction software such as REW and Dirac to be helpful if ideal placement is not possible or if the room has some bad modes. But this process presumes that the speaker was designed correctly.
I understand that some people will disagree with me on this.
To your original question, I think that a pair of 86 dB sensitivity woofers, in parallel, would mate up nicely with a 87 dB sensitivity midrange.
j.
I hope you meant to say 86dB and 16Ω. That matches the 87dB mid very well and yes, the amps have plenty of voltage headroom to drive a 16Ω system to Xmax.
Even if you only bake in 4db baffle step compensation (BSC), the two woofers in parallel (combined, 4 ohm) will be 88db sensitivity.
But...your midrange will get some boost from the woofer and tweeter when everything is combined. I think this is usually 1 to 2db. So even with only 4db BSC you'd be okay. With a full 6db BSC you'll probably still ending up padding your midrange down a little.
But...your midrange will get some boost from the woofer and tweeter when everything is combined. I think this is usually 1 to 2db. So even with only 4db BSC you'd be okay. With a full 6db BSC you'll probably still ending up padding your midrange down a little.
Thanks for the correction, that is what I meant 🙂.
I appreciate all the replies, I'll (probably) build a test cabinet and go for it. The only caveat is that I might do this active using DSP plate amps, then none of this will matter at all lol.
I've been called a bit of a bass head anyhow, so even though it might be a tad sacrilegious to say this here... having a dB or 2 bump in the boom region (as long as I can avoid it in the midbass) wouldn't be all that offensive in my opinion 😊
The forum software does not let you quote the very last post. The idea is that it will be clear if you're replying to that last post. I hate this particular feature.
I agree. While I'm not normally into recommending off script EQ without a solid reason, a broad shelf placed carefully in the bass can be done without creating a problem.
Sorry to correct you but it matters in this case.. sensitivity seems to be the word you're looking for.
.. and this is a reason to avoid using the word "loss" when talking about a practical baffle step.
One more... In the past I never considered this very deeply, but that's an eye opening statement. I understand the concept of "baffle step compensation", but thinking of it this way (it isn't necessarily a "loss") gives a clearer understanding of what is actually going on. Lots of physics involved in figuring out what your statement actually means, but for anyone looking for a deeper understanding of loudspeaker design and frequency response, it's worth looking into.
As far as my original question about the efficiency gap between an 87 dB sensitive midrange and 92 dB sensitive woofers, the general consensus here is... go for it, it will probably work 🙂
True! And you always can switch to the series option (as I once did long ago, combining 10” woofers with a 7” mid).