Thank you.
So they recommend 4 cubic-inch - guess that's ported.
You give it around 5,5 and 7,5 closed.
I remember you talked about the way you use drivers a bit differently than usual, because these roll off very quickly.
So by having 5 x 15" in a "small" room - suddenly we can ignore the classical goal of 0,7Q for a given driver in a given box - cause it's subwoofer duty and there is no term called fast/firm/tight bass?
I allready play with 4 subwoofers for years - nice even FR and good blend with the mains - almost exactly via the recipe you've always explain in your videos and here.
12" Peerless/ScanSpeak drivers in closed 4 cubic boxes. But after I experienced how 15" and 18" drivers with ease, can energize the very deep octave - even at low volume. Then I simply wish for a bit more - and thought maybe I should give pro drivers a go.
So they recommend 4 cubic-inch - guess that's ported.
You give it around 5,5 and 7,5 closed.
I remember you talked about the way you use drivers a bit differently than usual, because these roll off very quickly.
So by having 5 x 15" in a "small" room - suddenly we can ignore the classical goal of 0,7Q for a given driver in a given box - cause it's subwoofer duty and there is no term called fast/firm/tight bass?
I allready play with 4 subwoofers for years - nice even FR and good blend with the mains - almost exactly via the recipe you've always explain in your videos and here.
12" Peerless/ScanSpeak drivers in closed 4 cubic boxes. But after I experienced how 15" and 18" drivers with ease, can energize the very deep octave - even at low volume. Then I simply wish for a bit more - and thought maybe I should give pro drivers a go.
Hi Earl,
thanks again for all the info you've shared in this thread!
I was watching your talk at SMWTMS on updating your home theater from a few years ago.
Earl Geddes Updates His Home Theater - YouTube
I came across the portion of the video where you mentioned having trouble with a new at the time $1500 Yamaha receiver. I had actually been looking at Yamaha receivers as an option but would have to rule them out if they won't work for multi subs. Did you work out the issue you had with your Yamaha in the end? I didn't follow exactly what the issue was. You said you had trouble with or couldn't get the sub outs to work because they assumed a crossover. I know you do use a LPF on the subs while running the mains full range, so was the problem that the sub out wouldn't allow a high enough cutoff on the LPF side? Or was it that it would also HPF the other "non sub" channels?
What I had been hoping to use to feed a minidsp for the subs would be the stereo Zone preamp outs . My understanding is the zone outputs are supposed to be a stereo mixdown of all the other channels including the LFE which sounded like the perfect option to use for one of the 4x2 HD miniDSP's since they only have 2 inputs. Is this actually what you ended up using, or some totally different setup altogether? Otherwise I was going to consider the much more expensive 10x10HD or the Dayton DSP 408. The Dayton is much cheaper from Parts Express and has 4 inputs, not enough to cover all the channels but enough to mix L,R,C, and LFE if it can't be done correctly in the receiver.
thanks,
Dan
thanks again for all the info you've shared in this thread!
I was watching your talk at SMWTMS on updating your home theater from a few years ago.
Earl Geddes Updates His Home Theater - YouTube
I came across the portion of the video where you mentioned having trouble with a new at the time $1500 Yamaha receiver. I had actually been looking at Yamaha receivers as an option but would have to rule them out if they won't work for multi subs. Did you work out the issue you had with your Yamaha in the end? I didn't follow exactly what the issue was. You said you had trouble with or couldn't get the sub outs to work because they assumed a crossover. I know you do use a LPF on the subs while running the mains full range, so was the problem that the sub out wouldn't allow a high enough cutoff on the LPF side? Or was it that it would also HPF the other "non sub" channels?
What I had been hoping to use to feed a minidsp for the subs would be the stereo Zone preamp outs . My understanding is the zone outputs are supposed to be a stereo mixdown of all the other channels including the LFE which sounded like the perfect option to use for one of the 4x2 HD miniDSP's since they only have 2 inputs. Is this actually what you ended up using, or some totally different setup altogether? Otherwise I was going to consider the much more expensive 10x10HD or the Dayton DSP 408. The Dayton is much cheaper from Parts Express and has 4 inputs, not enough to cover all the channels but enough to mix L,R,C, and LFE if it can't be done correctly in the receiver.
thanks,
Dan
I hate to trash any manufacturer but that Yamaha was terrible. What I disliked most was its inflexibility. I was made assuming the user wanted the device to do everything automatically. Want to do things differently - no way!!
My old friend Dave Clark also had the same experience with Yamaha. We both ended up selling them at a great financial loss.
Normally I think the world of Yamaha products, but in the receiver arena, I'd stay away. I bought a Pioneer. Still had to modify it.
My old friend Dave Clark also had the same experience with Yamaha. We both ended up selling them at a great financial loss.
Normally I think the world of Yamaha products, but in the receiver arena, I'd stay away. I bought a Pioneer. Still had to modify it.
That's disappointing to hear.
Do you use one of the miniDSP models with 2 inputs? If so, do you just feed it L/R signals or do you have a mixdown of all channels+LFE available? Or do you have a 10x10HD that you can send all individual channels and mix to mono within miniDSP?
Have you had any issues with clipping at the inputs of the miniDSP due to its +/-2V range?
thanks,
Dan
Do you use one of the miniDSP models with 2 inputs? If so, do you just feed it L/R signals or do you have a mixdown of all channels+LFE available? Or do you have a 10x10HD that you can send all individual channels and mix to mono within miniDSP?
Have you had any issues with clipping at the inputs of the miniDSP due to its +/-2V range?
thanks,
Dan
Hi,
I am aware that the mic needs to be moved around to get an average response around the listening area, but in case one wants to measure by fixed mics at various locations near listening area then how many mics (locations) are needed, minimum, to get a good average?
Thanks and Regards,
WA
I am aware that the mic needs to be moved around to get an average response around the listening area, but in case one wants to measure by fixed mics at various locations near listening area then how many mics (locations) are needed, minimum, to get a good average?
Thanks and Regards,
WA
If you are just incrementing iteratively the EQ, just one location is needed to observe the changes.
I have just one good chair and use a mic stand and three spots across the backrest about 8 inches apart. What happens elsewhere in the room not important. But you must do L and R separately. Also do all playing to see where L and R add up negatively.
But a mic FR and human experience not the same, even if you could coordinate to a a Fletcher-Munson curve.
Post your results. REW takes snapshots of overlay plots that post easy.
I have just one good chair and use a mic stand and three spots across the backrest about 8 inches apart. What happens elsewhere in the room not important. But you must do L and R separately. Also do all playing to see where L and R add up negatively.
But a mic FR and human experience not the same, even if you could coordinate to a a Fletcher-Munson curve.
Post your results. REW takes snapshots of overlay plots that post easy.
Originally, the Geddes Approach was two mains and three low frequency sources: one ultra-low frequency (bandpass) and two broadband low frequency sources.
It looks like it evolved into two mains with five low frequency sources.
Did that happen because three closed sources were required to match the work of the ultra low frequency bandpass source?
I never changed anything actually, It's always been 3 subs, well now they are all about the same because I just EQ them so their individual responses don't really matter. And then three mains with 15" woofers, actually you could think of this as all the same driver in two different box volumes, all monopoles and each individually EQ'd for best response.
As to the number of spatial points required, its a complex formula that involves the error uncertainty, the frequency averaging done and the frequency. For example; third octave at LFs requires only one mic, narrowband measurements like FFTs take two or three down to the lowest frequency and at least 6 for the HF's. This is for about a 3 dB variance.
Think of it this way, at very long wavelengths you need a large distance to get much change in pressure, it doesn't vary much with distance, but at 10 kHz an inch is a factor. You have to average out these minute spatial variations to get a reliable result.
As to the number of spatial points required, its a complex formula that involves the error uncertainty, the frequency averaging done and the frequency. For example; third octave at LFs requires only one mic, narrowband measurements like FFTs take two or three down to the lowest frequency and at least 6 for the HF's. This is for about a 3 dB variance.
Think of it this way, at very long wavelengths you need a large distance to get much change in pressure, it doesn't vary much with distance, but at 10 kHz an inch is a factor. You have to average out these minute spatial variations to get a reliable result.
From post 1696
I've been wondering about why and when one would use nearfield subs. Maybe they supply their greatest benefit when you can't modify the room.
I've been wondering about why and when one would use nearfield subs. Maybe they supply their greatest benefit when you can't modify the room.
I disagree with the sealed vs bandpass argument.
If a speaker moves, then it distorts. A speaker moves less in a BP than Sealed per a given voltage. That gives way to BP is more efficient than Sealed. BP does not need the same amount of amplifier power as Sealed to get to the required loudness. If you have room multiple Sealed, then you have room for at least half as many BP's and be just as loud or louder.
Two $500 subs + $200 in build materials for 2 sealed enclosures + two $500 amps = $2,200.
One $500 sub + $200 in build materials for one BP6 enclosure + one $500 amp = $1,200.
It's possible you might spend $4,400 in Sealed to beat the $1,200 BP setup.
Once above the tuning band, both boxes are similar.
Just above tuning, the BR gets a boost from the port (AKA boom).
But bellow tuning, the output from the port is anti-phase and so the BR loses output (not too "efficient" there, eh). BP1Fanatic seems to have overlooked that fact.
The air which is sealed in the sealed box acts as a spring (believed to be linear). Which leads to cleaner bass. Unlike BR.
With all the ups and downs of the BR freq response, you can't expect an FR which is smooth or simple, blind faith in sims not withstanding.
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Based on my measurements (I analyze my builds by looking at their THD curves as well as FR an impedance), I'm pretty sure that most drivers start producing distortion as soon as their cones start moving
.The question really should be if the distortion is appreciable (measured) and noticeable (subjective). 10% measured THD at low bass frequencies could be considered appreciable, but whether or not it's noticeable is another matter - that's basically up to the listener and what frequency range we are talking about.
In general, I've found that different subwoofer alignments have different THD profiles, which generally have a lot to do with how the driver is loaded. 4th order bandpass alignments have the advantage of cutting a lot of the distortion generated in the passband by passing it through an acoustic filter, which results in pretty unique "THD profile" that perhaps accounts for part of the reason that it sounds "different". This THD profile could give the impression that it could be played louder before distortion becomes noticeable.
For example, I've attached a THD profile for my Enigma build, driven up to 10% THD in its passband (40 Hz to ~110 Hz). The "acoustic filter" seems to do a pretty good job of controlling distortion down to just above 50 Hz. Below that, the filter is no longer working to help reduce distortion and THD starts rising quickly. BTW, that THD peak around 170 Hz? That was caused by a rattling circuit board inside the enclosure (a passive two-stage limiting circuit that I added in series with the driver - to give it a bit more survivability, seeing that the Enigma was going to be used in my brother's bar as part of the background music system). The rattling circuit board was subsequently dealt with
. It may be possible to improve that THD profile 4th order BP alignment even further by "augmenting" the design with a small internal internal vent to introduce another driver displacement minimum, this one below the passband, the purpose being to reduce driver excursion more than increase output and/or widen its passband. Something I wanted to experiment with, but alas, the Enigma is already in use...
As for efficiency, that's an interesting question. Would a sealed alignment and a 4th order bandpass alignment with the same net volume and the same -3dB point have the same efficiency? One is a 2nd order alignment and the other is a 4th order alignment....
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