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Old 26th May 2008, 02:24 PM   #211
publius is offline publius  United States
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Quote:
Originally posted by gedlee


Each sub does not cover a different frequency range. One does, in my case, but that not necessary. The 15's go down to about 50 Hz, monopoles with a natural rolloff. There is one very LF sub 25 - 50 Hz. one broadband sub 50-100 and another 50 - 150. So at about 50 Hz there are five sources, one below that, four to about 100 Hz, three to 150 Hz and then just the mains.

The subs feed from the LFE channel on the receiver.

My room is a home theater.

THX is not the gospel in audio.
This is the most screwed up system that I have ever heard, but you are E.G. and I am nobody, so I feel compelled to try to understand why you have put it together this way.

Question 1: If you are not crossing any content to your subs and your mains roll off at 50hz, how do you hear content below 50hz that is in the music? I know there is not much content below 50hz, but still, your system would appear to be incapable of reproducing the bottom octave on a piano and I am guessing that is not right.

Question 2: The Dolby LFE channel spec has a brickwall at 120hz, so there is no content above 120hz for the sub that is crossed at 150hz. What is the purpose of the low pass filter on this sub?

Question 3: Given that deep bass requires much more power and displaced air than upper bass, why do you have two subs (and two speakers) covering the upper bass and only one unit covering the deep bass? Seems like the sub that is not playing any content in the LFE channel from 120hz and up could be better deployed assisting below 50 hz.

I am completely baffled by your configuration, I admit that I don't understand your approach, and I apologize if my questions are poor questions.
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Old 26th May 2008, 02:35 PM   #212
gedlee is offline gedlee  United States
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Question 1: You do misunderstand, there is a sub specifically tuned to do 25-50 Hz. Reread my post.

Question 2: This is not true. The LP filter in the LFE is tunable and on my receiver it can go up to 150 Hz.

Question 3: I use multiple subs to smooth out the LF mode problems in a small room. I have more than enough SPL capability for any situation and in fact the biggest problem with this approach is getting too much low end. Balancing all this out correctly is not trivial and I posted that point elsewhere when we talked about multuiple subs in the "cardiod bass" thread. You should go read that one.

There is no "one right way" to set the subs paramters (gain, filters, phase). You take the subs that you have and set them up in the room with measurements. If you have enough subs you will usually get something satisfactory. Too few subs and you will always be disappointed.
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Old 26th May 2008, 03:08 PM   #213
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There is no "one right way" to set the subs paramters (gain, filters, phase). You take the subs that you have and set them up in the room with measurements. If you have enough subs you will usually get something satisfactory. Too few subs and you will always be disappointed.
Thank you. I wholeheartedly agree.

Anand.
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Old 26th May 2008, 09:16 PM   #214
limono is offline limono  United States
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Seems like this going to be SOTA speaker kit and I only wished dear DR provided plans for proper woofer to compliment satelites.
Somehow I'm not convinced in matching some Costco Booomer to
Summas 80-100 Hz.
Regards, L
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Old 26th May 2008, 10:02 PM   #215
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Quote:
Originally posted by gedlee
Question 3: I use multiple subs to smooth out the LF mode problems in a small room. I have more than enough SPL capability for any situation and in fact the biggest problem with this approach is getting too much low end. Balancing all this out correctly is not trivial and I posted that point elsewhere when we talked about multuiple subs in the "cardiod bass" thread. You should go read that one.
Here's the thread: Cardioid Bass
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Old 26th May 2008, 10:06 PM   #216
gedlee is offline gedlee  United States
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Quote:
Originally posted by limono
Seems like this going to be SOTA speaker kit and I only wished dear DR provided plans for proper woofer to compliment satelites.
Somehow I'm not convinced in matching some Costco Booomer to
Summas 80-100 Hz.
Regards, L

Summas are 50Hz and up. I will supply plans for my subs thats not a problem, but I won't make them as kits since thats just a waste of my time considering the economics.
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Old 26th May 2008, 10:23 PM   #217
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Quote:
Originally posted by limono
Seems like this going to be SOTA speaker kit and I only wished dear DR provided plans for proper woofer to compliment satelites.
Somehow I'm not convinced in matching some Costco Booomer to
Summas 80-100 Hz.
Regards, L
Could someone explain to me the advantage of using a boutique subwoofer instead of a Costco subwoofer?

You might argue that the Costco sub will have lousy power handling. If that's the case, buy four of them. That increases your SPL limit by 12db.

You might argue the Costco sub isn't as handsome as an audiophile sub. That may be true, so hide it! No one wants to look at three subs anyways.

You might argue that the Costco sub has lousy frequency response. While some cheap subs are designed with a hump in the midbass, there are plenty of inexpensive powered subs that measure well and have predictable crossovers and EQ built in.

Last but not least is price. Spending $750 on three Costco subs and pairing them with a $1200 kit seams reasonable. Spending $3000 on three boutique subs seems unnecessary with $1200 mains.

I've always been mystified by the use of exotic subwoofers in the home. In car audio, they make a lot of sense, because box size is king in mobile audio. Also, car subs function in "pressure mode" due to the small dimensions of the cabin. Exotic subs also make sense in pro audio, where dozens of subs are in play and each is being fed thousands of watts.

In the home, not so much.
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Old 26th May 2008, 10:56 PM   #218
limono is offline limono  United States
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Well , sorry but by Summa I meant 10" dIY version which is 80-100 Hz and needs a woofer not subwoofer to be a regular full range speaker. Maybe it's time to name the kit ??I agree that for HT the quality of subwoofer is of no importance and most everything will do. Sorry to add a confusion to already confused thread .
Regards, L
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Old 26th May 2008, 11:45 PM   #219
publius is offline publius  United States
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Quote:
Originally posted by gedlee
[B]Question 1: You do misunderstand, there is a sub specifically tuned to do 25-50 Hz. Reread my post.
I have read and re-read your posts in this thread. You have a sub tuned to do 25-50hz. BUT, you said that this sub is receiving the LFE channel source. The *LFE channel* is different from the *subwoofer channel*.

Since you have said in a previous post that you "do not cross to the subs", then the only content that your subwoofer array is receiving is that which is contained in the LFE channel. If you are listening to a two-channel source, such as a piano recording, there will be no content in the LFE channel and in your system you will hear not hear the bottom octave of the piano (~27-51hz).

Quote:
Originally posted by gedlee
Question 2: This is not true. The LP filter in the LFE is tunable and on my receiver it can go up to 150 Hz.
I think that you are confused. The LFE channel and the subwoofer channel are two separate sources of content though they are summed and fed through the same cable to the subwoofer. In a previous post you said that you "do not cross to subs". This indicates that you are running your main speakers full range and that no content is being shifted from the main channels to the subwoofers. In such a system, the subwoofer(s) will receive only the LFE (aka ".1") content. Dolby has a low-pass filter for LFE content at 120hz. There is no slope. All content above 120hz is just filtered out. So nothing is gained by setting the LFE LP filter on your receiver to 150hz.

Quote:
Originally posted by gedlee
Question 3: I use multiple subs to smooth out the LF mode problems in a small room. I have more than enough SPL capability for any situation and in fact the biggest problem with this approach is getting too much low end. Balancing all this out correctly is not trivial and I posted that point elsewhere when we talked about multuiple subs in the "cardiod bass" thread. You should go read that one.
Thank you for pointing out the cardiod bass thread. I will be sure to read through.

It remains an open question though how you can have "too much lowend" when you are only powering your subs with the LFE content channel.

Perhaps what you are really doing is:

1. running your main speakers full range (and letting their natural rolloff below 50hz protect them from overdrive)
2. using your receiver to SUM content from your main speaker channels below 150hz to the LFE channel, creating what is called a subwoofer channel (which is distinct from an LFE channel).
3. using this subwoofer channel as the input for each of your subwoofers, which you then adjust for frequency and level.

If this is the case, then it would all seem to make some sense.

Quote:
Originally posted by gedlee
There is no "one right way" to set the subs paramters (gain, filters, phase). You take the subs that you have and set them up in the room with measurements. If you have enough subs you will usually get something satisfactory. Too few subs and you will always be disappointed.
Yes. Parametric EQ can also help as well. Do you have parametric EQ in your subwoofers? If not, how do you deal with room modes?

[EDIT: I see (in another thread) that structural methods are used to tame modes. Nice.]
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Old 26th May 2008, 11:58 PM   #220
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Quote:
Originally posted by limono

I agree that for HT the quality of subwoofer is of no importance and most everything will do. Sorry to add a confusion to already confused thread .
Regards, L

HT is the ONLY place a subwoofer matters. You don't need one for music, providing you have real main speakers.

Good quality subs beat one note boom boxes and over eq'ed, over driven poop producers any day.
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