I realize that you still working out the kinks ... interested in the reproduction quality of the grs music wise. I'm interested in doing a dual U frame as detailed by Jack. These drivers are definitely priced right.
Keep us posted
Let us know if you build 'em w the GRS, at that price, if the performance is anywhere near what the Eminence it'll be an astronomically good QPR
Let us know if you build 'em w the GRS, at that price, if the performance is anywhere near what the Eminence it'll be an astronomically good QPR
Hey all, Sorry for the late reply.Yes, worked out very nice. Just as Jack previously indicated - the ML Depth goes a bit lower, but the GRS has the upper bass.
Only thing I wasn't impressed with is the build quality - I bought five drivers (had a 15" Fender bass amp to repair - blown driver - for a friend and figured why not use these).
On two of the drivers the frames were distorted / warped and not flat - but after they were bolted up tight, they flattened out. I have a little issue with one speaker / driver - can't tell if its the baffle that is vibrating or voice coil rubbing - I am thinking the former...
But all in all, at $24 each and a few bucks for wood, stain and feet, worked out very nice.
I currently have it on a 2nd order Butterworth at 120hz between the CLS. Still working out the Behringer - I have a love hate relationship with the Behringer.
Also fixed a ML Dynamo 700 plate amp (300 wpc) and will try it out on a pair of these drivers...
Only thing I wasn't impressed with is the build quality - I bought five drivers (had a 15" Fender bass amp to repair - blown driver - for a friend and figured why not use these).
On two of the drivers the frames were distorted / warped and not flat - but after they were bolted up tight, they flattened out. I have a little issue with one speaker / driver - can't tell if its the baffle that is vibrating or voice coil rubbing - I am thinking the former...
But all in all, at $24 each and a few bucks for wood, stain and feet, worked out very nice.
I currently have it on a 2nd order Butterworth at 120hz between the CLS. Still working out the Behringer - I have a love hate relationship with the Behringer.
Also fixed a ML Dynamo 700 plate amp (300 wpc) and will try it out on a pair of these drivers...
Clarification?
Your comment about having the upper bass - does this mean you like the upper bass quality on the OB vs the ML depth? - that's what I'm thinking it means, but is it?
Yeah, build quality is not the greatest. Lots of room for improvement, via stiffening and damping of the baskets, if you have the patience for tweaking.
In your pix it looks like you've kept it as a simple OB. Have you tried the u-frame?
Your comment about having the upper bass - does this mean you like the upper bass quality on the OB vs the ML depth? - that's what I'm thinking it means, but is it?
Yeah, build quality is not the greatest. Lots of room for improvement, via stiffening and damping of the baskets, if you have the patience for tweaking.
Jack,
The Depths do not go any higher than 80hz, while I have the Baffles coming in at 125hz. I can't really fault the Depths for Mid / Upper Bass, but I am content with what the GRS can do.
I was going to try the U frames next. Do you think it would be a marked improvement over the OBs?
The Depths do not go any higher than 80hz, while I have the Baffles coming in at 125hz. I can't really fault the Depths for Mid / Upper Bass, but I am content with what the GRS can do.
I was going to try the U frames next. Do you think it would be a marked improvement over the OBs?
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U-frames may be better
By virtue of having a more elevated bottom end than the plain OB, the U-frames should be able to play significantly louder. My estimate is you gain at least 6dB low-bass efficiency, and seeing as the excursion on these drivers is rather limited you should be able to hit peak levels that are substantially higher. Conversely, at the same SPL, the U-frame distortion should be a good bit lower.
The trade-off is that the undamped u-frame forms a bit of "short-horn" in the rear, and this creates a significant peak in the response. If you go back a few posts and look at Bjorno's sims, it shows rather prominently. BUT, as he also shows in the sims, if you use 0.25lb/ft3 of the fiberfill the peak smooths out quite a lot, and the fill increases the bass efficiency by +2db or so at 30Hz. On Bjorno's sims the 30Hz efficiency looks to be about 92dB, which is phenomenal for a box this size. (IIRC, the dual OB using the same drivers sims out about 85 - 86dB efficiency).
It means that once eq'd flat, you'd have a sub that operates with about 92dB efficiency across the band, with -3dB point near 28 Hz. AND, because it has that very desirable cardioid response, it will be much less prone to excite the lateral and vertical modes in the room. (OB does this too due to its figure 8 response, but the u-frame has that great gain in efficiency.)
Also, the eq slope is a lot gentler, meaning a lot less power will be wasted.
It's a win-win-win scenario except for the additional complexity of building a strong u-frame enclosure - the force-canceling arrangement requires very solid construction... but then again so would a conventional sealed or vented box sub.
Aside from the gains mentioned above, mounting the drivers back-to-back cancels out most cabinet transmitted vibrations and very substantially reduces the amount of architecturally transmitted bass. This is a HUGE factor, ignored by most, and once you hear the difference, you may never want to go back.
So yes, my bet would be that you (and most others) would probably like the opposing side-mounted force canceling u-frame version even better.
By virtue of having a more elevated bottom end than the plain OB, the U-frames should be able to play significantly louder. My estimate is you gain at least 6dB low-bass efficiency, and seeing as the excursion on these drivers is rather limited you should be able to hit peak levels that are substantially higher. Conversely, at the same SPL, the U-frame distortion should be a good bit lower.
The trade-off is that the undamped u-frame forms a bit of "short-horn" in the rear, and this creates a significant peak in the response. If you go back a few posts and look at Bjorno's sims, it shows rather prominently. BUT, as he also shows in the sims, if you use 0.25lb/ft3 of the fiberfill the peak smooths out quite a lot, and the fill increases the bass efficiency by +2db or so at 30Hz. On Bjorno's sims the 30Hz efficiency looks to be about 92dB, which is phenomenal for a box this size. (IIRC, the dual OB using the same drivers sims out about 85 - 86dB efficiency).
It means that once eq'd flat, you'd have a sub that operates with about 92dB efficiency across the band, with -3dB point near 28 Hz. AND, because it has that very desirable cardioid response, it will be much less prone to excite the lateral and vertical modes in the room. (OB does this too due to its figure 8 response, but the u-frame has that great gain in efficiency.)
Also, the eq slope is a lot gentler, meaning a lot less power will be wasted.
It's a win-win-win scenario except for the additional complexity of building a strong u-frame enclosure - the force-canceling arrangement requires very solid construction... but then again so would a conventional sealed or vented box sub.
Aside from the gains mentioned above, mounting the drivers back-to-back cancels out most cabinet transmitted vibrations and very substantially reduces the amount of architecturally transmitted bass. This is a HUGE factor, ignored by most, and once you hear the difference, you may never want to go back.
So yes, my bet would be that you (and most others) would probably like the opposing side-mounted force canceling u-frame version even better.
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OK, bought the additional wood for the U frames. Hopefully have some time this weekend to build everything up and give a listen...
OK, I built the U-Frame. I used a U frame that is 10" wide x 18" high x 16" wide and wide open in back. At 10" wide, the magnets touch and after tightening the bolts, seem to be solid connection between the two back magnets.
Initial impressions were not good. SPL was a far bit less than the open baffles.
I have a feeling that this is due to the magnets being somewhat compressed together and the back vent holes are now blocked, not allowing the speakers to move freely...I tried wiring push push and push pull and the push pull definitely sounded better confirming the vent hole issue...damn, what was I thinking trying the 10" wide?
Anyway, I will be going out tomorrow and picking up some 12" wide MDF and trying it again...
Initial impressions were not good. SPL was a far bit less than the open baffles.
I have a feeling that this is due to the magnets being somewhat compressed together and the back vent holes are now blocked, not allowing the speakers to move freely...I tried wiring push push and push pull and the push pull definitely sounded better confirming the vent hole issue...damn, what was I thinking trying the 10" wide?
Anyway, I will be going out tomorrow and picking up some 12" wide MDF and trying it again...
Built another U-Frame with 12" panels and only marginally better. I went back and forth listening to the OB and the U-Frame and I must say I prefer the OB. They are more clear, and seem to go just as deep and as loud as the U-Frame. Front firing is definitely prefered for my tastes.
I cut one of the OB in half for the U-Frame (damn) and will have to build another...so I put the ML Depth back in - forgot how clear and deep these sound. I may just call it a day and keep the Depth in the system.... maybe pick up another someday...
I cut one of the OB in half for the U-Frame (damn) and will have to build another...so I put the ML Depth back in - forgot how clear and deep these sound. I may just call it a day and keep the Depth in the system.... maybe pick up another someday...
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