Are three inexpensive subs better than one expensive sub-Dr. Earl Geddes Approach - Page 57

Originally Posted by gedlee

No, Randy was not one of the people who posted a review. The names of the people are all there.

I'll post some "pictures" soon, but they are not conclusive yet about much of anything. Only to show that I have some data, just not yet enough to be comprehensive. And all of this is very time consuming and tiem is not something that I have in abundance.

Originally Posted by gedlee

No, Randy was not one of the people who posted a review. The names of the people are all there.

I'll post some "pictures" soon, but they are not conclusive yet about much of anything. Only to show that I have some data, just not yet enough to be comprehensive. And all of this is very time consuming and tiem is not something that I have in abundance.

Originally Posted by Randybes

I don't think you understand that Dr. Geddes is a scientist. As such, he is not going to just post measurements without looking at what those measurements mean and why. I would guess we have spurred him on to doing some work on this whole subject which is a good thing. I get the feeling this is more of a challenge to his credentials than it is really wanting to see some random measurements of his room. More of a 'he must be hiding something" which I don't think is the case at all. I watched him take polar response measurements of the speakers I bought from him (which he would take of every speaker he builds). How many polar response measurements have you seen posted by any speaker manufacturer? He is very careful about what he does and how he does it.

Also, who is "your panel"?

Originally Posted by penngray

We simply like to have lots of data in front of us to support any subjective conclusions and we are blunt about wanting it. I like blunt opinion, no tap dancing around to stroke any egos because no egos need to be stroked.

That is all, no one should really take offence to people posting "We want measurements or this is meaningless". The thread would have been better with them period.

Originally Posted by penngray

Relax, I winked but the point I was making was that you were one of the "12 strangers in the room" experiencing his setup, were you not?

I believe that is the "the panel" we are referring too, its the only evidence posted confirming how great the bass was.

Originally Posted by J_Palmer_Cass

I guess that brings us back to the beginning of the thread. Some people think that you need to use at least one mega sub to reproduce content below 20 Hz. I agree that is a side issue to a certain extent. My own ULF subwoofer is only good to 20 Hz.

I do not see the need to use more than one mega subwoofer if you are into very low ULF. Adding at least a few "inexpensive" subwoofers to a system that cover bass frequencies above 50 Hz is a sound approach in a lot of ways. What you do with the "inexpensive" subwoofers is up to the end user. In all cases, you have to know what you are trying to do with those subwoofers.

Seems to me that "inexpensive" subwoofers, bass bins, integrated subwoofers, and MBMs are all pretty much the same item!

Originally Posted by Randybes

I don't think you understand that Dr. Geddes is a scientist. As such, he is not going to just post measurements without looking at what those measurements mean and why. I would guess we have spurred him on to doing some work on this whole subject which is a good thing. I get the feeling this is more of a challenge to his credentials than it is really wanting to see some random measurements of his room. More of a 'he must be hiding something" which I don't think is the case at all. I watched him take polar response measurements of the speakers I bought from him (which he would take of every speaker he builds). How many polar response measurements have you seen posted by any speaker manufacturer? He is very careful about what he does and how he does it.

Also, who is "your panel"?

Originally Posted by gedlee

THEY ARE THE SAME METHOD!!!! The details of setup differ a little, but the major factors are identical.

Originally Posted by goneten

Toole does not eschew the use of randomly positioned subwoofers within a room for smoothest response.

Originally Posted by krabapple

I think you don't really mean 'eschew' here. To 'eschew' something is to 'not be in favor of it' . So if Toole 'does not eschew the use of randomly positioned subs' that means he accepts or endorses it.

Btw, I'm not sure that the 'Geddes method' calls for 'randomly' positioned subs either.

Originally Posted by gedlee

Here are two plots. First with only one sub set for lowest mean frequency deviation, about 2 dB SD.
http://www.gedlee.com/downloads/One_sub.pdf

Second is with three subs setup with a DCX2496 - abou 1 dB SD and obviuos lower frequency capability.

Both curves are three seats and average. Spatial variance is light blue line.

http://www.gedlee.com/downloads/all.pdf

Originally Posted by Nuance

Thanks for posting the FR plot, Geddes. It looks like you room certainly benefited from EQ.

Originally Posted by goneten

But we are talking about your specific method of reaching that conclusion, not that multiple subwoofers make a difference. Otherwise this thread would have died on page 1.

Please don't come here and tell me that I've perverted what you've said. One could say that all of these methods reach a common conclusion; smoother bass. But the way in which those methods reach that conclusion obviously differ. Tooles method for reaching smoother bass is obviously different from yours (for many reasons) therefore they cannot be one and the same method !

Regards,

Originally Posted by craig john

So, I assume the red, green and purple are the three seating positions, the black is the average and the light blue is the "spatial variance", is that correct? Could you explain how the "spatial variance" is calculated, please? It doesn't seem to be the same thing as "spatial average".

Also, do you feel that 3 measurement locations are enough to accurately and completely calculate the "spatial variance"? And could you describe the 3 spatial locations in relation to the subwoofer placements and the seating.

Finally, which of the 3 subs is the ULF sub and which two are the 50 to 150 Hz subs? Is the sub in the first plot one of the 50 to 150 Hz subs?

Thanks.

Craig

Edit: Just thought of another question... Your second plot shows all three subs. I assume they are all playing at the same time. If so, how did you measure the response of each sub individually?

Originally Posted by craig john

I don't think he's using the EQ in the DCX. He's just using the gains and crossovers, is that correct Dr. Geddes?

Craig

Originally Posted by gedlee

"how did you measure the response of each sub individually?" Uh, by measureing them individually!!? Turn all the others off!!

Originally Posted by gedlee

I have said all along that it is the use of multiple subs that is the big factor and that is generally NOT agreed to by the average audiophile.

Your claim that this is widely accepted practice is wrong, because its not.

Originally Posted by gedlee

I have said all along that it is the use of multiple subs that is the big factor and that is generally NOT agreed to by the average audiophile. Your claim that this is widely accepted practice is wrong, because its not.

Originally Posted by goneten

Was there a study performed to determine whether the "average audiophile" agrees with the concept of multiple subwoofers?

Originally Posted by gedlee

Here are two plots. First with only one sub set for lowest mean frequency deviation, about 2 dB SD.
http://www.gedlee.com/downloads/One_sub.pdf

Second is with three subs setup with a DCX2496 - abou 1 dB SD and obviuos lower frequency capability.

Both curves are three seats and average. Spatial variance is light blue line.

http://www.gedlee.com/downloads/all.pdf

Originally Posted by goneten


Was there a study performed to determine whether the "average audiophile" agrees with the concept of multiple subwoofers ? Please point me to that study.

Originally Posted by gedlee


In talking with Floyd about this he has no problem with letting the subs be placed as they "can be" and then optimizing under that constraint. Hence he has never disagreed with what I do, he just hasn't any experince with it.

Originally Posted by goneten

Was there a study performed to determine whether the "average audiophile" agrees with the concept of multiple subwoofers ? Please point me to that study.



My claim was directed more towards the AVS community than anything else. Most of us have an interest in this field and want to learn more. I think a large percentage of posters on this forum understand the theoretical benefits when using multiple subwoofers and some can put that theoretical knowledge into practice.

Actual evidence trumps theory every time in any case. What some disagree with are the finer details like, for instance, using multiple dissimilar subwoofers.

I, for one, don't agree with it but then my goals are not the same as yours. I value other things besides just smoothest bass at the listening position.

Regards,

Originally Posted by J_Palmer_Cass

You don't need a study for that. People can not even agree on what qualifies as a subwoofer. This very thread is a study on that issue!

Originally Posted by mjg100

I like the idea of using a ported sub for the ULF and sealed subs for the mid and upper bass. I think it is an efficient way of getting good bass.

Originally Posted by gedless

NO, my method is not completely random. Your characterization of what I say is quite often incorrect. Is there a reason for this?

Originally Posted by KyleLee

great point, this is a good line of thought and i agree, but many miss the ball on understanding what really makes good upper bass.... efficiency and low inductance is the ticket and technically they are one and the same.......nothing against ID subwofers or the ULS, but it has the inductance of a higher excursion woofer and only decent (not poor) sensitivity inline with again, high excursion woofers... its really much better for lower end stuff (im gonna get flamed for this one) but my point is, if you really want to pound @ 100Hz, you'll need to consider pro woofers that pull 95's and above (maybe even higher) Really a different kind of driver, and I'm gonna say this agian, the ULS is an awesome subwoofer, but its really a full range bass deal with very high xmax, and you can take the top subwoofers around and I will promise none of them are going to be great for upper bass AND very low bass at the same time. You can’t really do high xmax and high SPL easy... trust me, i have tried! I just blew 8 grand on a new patent this year that gets me about 1% closer to that goal so it’s not like I’m clueless over here with my lowly Bachelor of Science degree…. Speaking of degrees……no one in this thread is asking the REAL question: Why is Doctor Earl Geddes using cheep subwooers? I know you have re$ource$ Dr.…….

haha

Originally Posted by Nuance

I am hoping that the Acoustic Elegance AV15H drivers will solve that problem. They have great upper bass at the expense of only reaching down to about 15Hz. A pair of DIY AV15H's with a ULF ported subwoofer should solve the low bass and upper bass problem, though, no? After all, this thread is about the use and implementation of multiple subwoofers.

"The following shows the AV15X, H, and the SDX15 in 3.75cf with 500W. SDX15 is orange, AV15X is red and AV15H is green. "



Link

Originally Posted by KyleLee

its kind of a myth that drivers cant reach down to 15hz because of a constant voltage fr response, you need to consider EQ. The thing is take a very low Q driver that rolls off quick, it will have very poor bass response, or does it??. In fact, it's still more efficient than the same driver with a higher Q from less BL (for example). The higher Q driver may have outstanding low end response when you model it, but its not more "efficient," in terms of true energy in, SPL out, even in the low end. the simply difference is the amount of power (not voltage) required to driver to speaker. For a simple test you can run a frequency response with a constant power amplifier and you'll see that low Q driver with higher sensitivity still beat out low sensitivity drivers with high Q at all frequencies.
So when you compare FR response in bassbox, winsid or some other program, they don't show true potential considering constant energy.

I would argue the real limit for a driver with very high sensitivity to hit very low frequencies is not its Fs, its not its Qts, but its simple xmax.