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Author Topic: Suggestions for upgrade  (Read 5417 times)

Brad Weber

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Re: Suggestions for upgrade
« Reply #10 on: September 06, 2011, 10:48:34 pm »

I would change things around...first off I would run the Peavey bridged amps one each on the subs.
Keep in mind that when you bridge an amp
and have long cable runs you are drastically affecting damping.  There are other reasons NOT to bridge an amp and run high power.  If you are going to bridge then
put the bridged amps on the subs.
Is this being suggested in order to support the two extra mains you suggested, which would apparently be in parallel with the currant mains and thus present a nominal 4 Ohm rather than 8 Ohm total impedance?  Otherwise it would seem to result in using in less power from a less capable amp for the subs when the primary issue is apparently not enough bass and kick drum.  Since you have the same load impedance and the same cabling whether the amp is in stereo or bridge mode, being bridge mode may have a negligible effect on the damping factor.

I would run the QSC on the JBL tops and get two more
identical tops and put them further down in the room facing down into the audience about 30ft on the sides of the room.
You can run the two JBLs you have up front
and the same JBLs on the sides further back in the room on the QSC with no
problems.
This might make sense in a long, narrow room with appropriate processing applied to the additional speakers but this room is apparently 60' deep and 45' wide and you would have no delay, separate level control, etc. for the second set of speakers.  Coverage was not noted to be a problem and this would seem to provide minimal, if any, potential improvement in coverage or levels for the kick drum and bass while adding significant additional combfiltering and timing issues over a broad frequency range.  In this application I just don't see the potential advantages offsetting the potential disadvantages.

Move the subs together one one side of the stage or the other or better
yet if you can run them together center stage.  You will have MUCH better bass
response and even response in the room by having both subs together in ONE spot.
Agreed, clustering the subs may help.  One reason I suggested trying the system run mono with just one set of speakers was to check on 'power alley' type issues that may be occurring being the split subs.
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Abel Duenas

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Re: Suggestions for upgrade
« Reply #11 on: September 07, 2011, 11:11:21 pm »

Is this being suggested in order to support the two extra mains you suggested, which would apparently be in parallel with the currant mains and thus present a nominal 4 Ohm rather than 8 Ohm total impedance?  Otherwise it would seem to result in using in less power from a less capable amp for the subs when the primary issue is apparently not enough bass and kick drum.  Since you have the same load impedance and the same cabling whether the amp is in stereo or bridge mode, being bridge mode may have a negligible effect on the damping factor.
This might make sense in a long, narrow room with appropriate processing applied to the additional speakers but this room is apparently 60' deep and 45' wide and you would have no delay, separate level control, etc. for the second set of speakers.  Coverage was not noted to be a problem and this would seem to provide minimal, if any, potential improvement in coverage or levels for the kick drum and bass while adding significant additional combfiltering and timing issues over a broad frequency range.  In this application I just don't see the potential advantages offsetting the potential disadvantages.
Agreed, clustering the subs may help.  One reason I suggested trying the system run mono with just one set of speakers was to check on 'power alley' type issues that may be occurring being the split subs.
Coverage and intelligebility have never been a problem because although the room doesn't have the best accoustics, the congregation is able to hear the music and the sermon perfectly. Now I do think there's a power alley because about a month ago I burned a subwoofer so just one was working and to me it seemed that the bass was better defined and had a little bit more kick to it. Could it be possible that although the subs are in phase they are canceling each other out due to the accoustics or resonance in the room? Im going to try and put the subs in a center cluster this weekend and see how it goes. Now since it seems that I have the VSX settings wrong if it's not too much to ask what settings would you use with the set up that we have? Any help would be tremendously appreciated :-)
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Stu McDoniel

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Re: Suggestions for upgrade
« Reply #12 on: September 08, 2011, 11:09:25 am »

Is this being suggested in order to support the two extra mains you suggested, which would apparently be in parallel with the currant mains and thus present a nominal 4 Ohm rather than 8 Ohm total impedance?  Otherwise it would seem to result in using in less power from a less capable amp for the subs when the primary issue is apparently not enough bass and kick drum.  Since you have the same load impedance and the same cabling whether the amp is in stereo or bridge mode, being bridge mode may have a negligible effect on the damping factor.
This might make sense in a long, narrow room with appropriate processing applied to the additional speakers but this room is apparently 60' deep and 45' wide and you would have no delay, separate level control, etc. for the second set of speakers.  Coverage was not noted to be a problem and this would seem to provide minimal, if any, potential improvement in coverage or levels for the kick drum and bass while adding significant additional combfiltering and timing issues over a broad frequency range.  In this application I just don't see the potential advantages offsetting the potential disadvantages.
Agreed, clustering the subs may help.  One reason I suggested trying the system run mono with just one set of speakers was to check on 'power alley' type issues that may be occurring being the split subs.
I assumed the original OP would have enough knowledge to apply delay
to the extra cabs placed towards the back of the room and thus did not feel
the need to go into great detail.  Yes long cable runs affect damping factor
in a big way on bridged amps.   Why not add the two extra JBL loudspeakers
midway back in the room with proper delay and xover the subs down lower?
Im thinking that letting the 15" 2ways handle from 80hz up will give the system
more punch? Put the 18" cabs in one spot in the room to handle 80hz and down.
Having four JBLs distributed in the room will also allow the system to cover
the room much better and not be driven so hard.   It makes more sense to have more loudspeakers covering the space and "turn it down"...especially in a church!
This is what I would do with the system and everyone has their own opinion of course. 
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Jonathan Johnson

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Re: Suggestions for upgrade
« Reply #13 on: September 08, 2011, 03:12:30 pm »

Coverage and intelligebility have never been a problem because although the room doesn't have the best accoustics, the congregation is able to hear the music and the sermon perfectly. Now I do think there's a power alley because about a month ago I burned a subwoofer so just one was working and to me it seemed that the bass was better defined and had a little bit more kick to it. Could it be possible that although the subs are in phase they are canceling each other out due to the accoustics or resonance in the room? Im going to try and put the subs in a center cluster this weekend and see how it goes. Now since it seems that I have the VSX settings wrong if it's not too much to ask what settings would you use with the set up that we have? Any help would be tremendously appreciated :-)

This is only anecdotal evidence since I can't explain the physics behind it.

A buddy discovered that when he stacked subs, he got better results in odd numbers. So one on top of another (two subs) did not provide as much "kick" as a single sub, and three subs in a stack was even better. He explained to me the physics behind it (he's an audiophile, but he IS also an engineer so he knows when to call BS) but I just don't remember.
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Taylor Phillips

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Re: Suggestions for upgrade
« Reply #14 on: September 08, 2011, 10:00:41 pm »

Now I do think there's a power alley because about a month ago I burned a subwoofer so just one was working and to me it seemed that the bass was better defined and had a little bit more kick to it. Could it be possible that although the subs are in phase they are canceling each other out due to the accoustics or resonance in the room?
I think that's definitely possible - especially if you got better sound with only one sub working.  Play some recorded music through the system with only one sub on, then play the same thing with both subs and see how different the low end sounds. 

Also, if they subs would just be too in the way clustered together in front of the pulpit, you could try just putting them closer together i.e. one just to each side of the pulpit stairs.  It may not be as effective as clustering them, but it should help with the low end phase cancellation and power alley.  Something else I thought of would be to cluster them together just to one side. 
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Brad Weber

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Re: Suggestions for upgrade
« Reply #15 on: September 09, 2011, 01:30:28 am »

This is only anecdotal evidence since I can't explain the physics behind it.

A buddy discovered that when he stacked subs, he got better results in odd numbers. So one on top of another (two subs) did not provide as much "kick" as a single sub, and three subs in a stack was even better. He explained to me the physics behind it (he's an audiophile, but he IS also an engineer so he knows when to call BS) but I just don't remember.

I've known and worked with many Engineers who are very smart people but whose technical expertise did not include audio or acoustics.  I guess it is possible to get such results but the scenarios I envision would depend on the effects of the physical spacing of one sub to another and the spacing of the subs relative to the surrounding surfaces, in other words the results would be a factor of aspects other than the number of subs being odd or even.
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Jonathan Johnson

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Re: Suggestions for upgrade
« Reply #16 on: September 09, 2011, 01:44:24 am »

This is only anecdotal evidence since I can't explain the physics behind it.

A buddy discovered that when he stacked subs, he got better results in odd numbers. So one on top of another (two subs) did not provide as much "kick" as a single sub, and three subs in a stack was even better. He explained to me the physics behind it (he's an audiophile, but he IS also an engineer so he knows when to call BS) but I just don't remember.
I've known and worked with many Engineers who are very smart people but whose technical expertise did not include audio or acoustics.  I guess it is possible to get such results but the scenarios I envision would depend on the effects of the physical spacing of one sub to another and the spacing of the subs relative to the surrounding surfaces, in other words the results would be a factor of aspects other than the number of subs being odd or even.
I'm sure there are many variables that come into play. I should stress that my friend's experience was with a particular sub design in a particular environment, and had specifically to do with stacking the subs. Nevertheless it may be worth investigating.
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