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Old 15th July 2009, 01:49 AM   #1131
jdubs is offline jdubs  United States
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Thanks Ed. Wishful thinking on my part, I suppose! I was just trying to stay reasonably small, given this is a small(er) system for my bedroom.

Any suggestions?

-Jim
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Old 15th July 2009, 01:58 AM   #1132
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Jim,

Size (and budget) are my concerns. I'm learning as
I go with the lower-priced options.

I would consider subs using drivers with sensitivity and/or power handling that are in the Harper's range. You should still be able to stay reasonably small.
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Old 15th July 2009, 04:22 AM   #1133
jdubs is offline jdubs  United States
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Thanks Ed. These PE subs stuck out given their HSU lineage. Hmmm...need to shop around more.

Anyone have any good ideas for small(er) subs that can keep up with a speaker like the Harpers?

Thanks,
Jim
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Old 15th July 2009, 08:03 AM   #1134
col is offline col  Australia
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you might want to read my post from the "Multiple Small Subs - Geddes Approach" thread:

http://www.diyaudio.com/forums/showt...13#post1872613

This method enables you to get low bass from a small sealed enclosure, if you have the right drivers.

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Old 15th July 2009, 12:40 PM   #1135
gedlee is offline gedlee  United States
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Default Re: Harper Status?

Quote:
Originally posted by jdubs
Earl, what's the latest on the Harper? Any more information and / or pictures?

I'd like a pair for a bedroom system. How much subwoofer do they need? Think a couple of these would do the trick?


Thanks!
Jim
Just finishing up a large batch of Harpers this week and will test this first production lot and ship. The Harpers are no where near as efficient as the bigger speakers, but I do find that the large number of inexpensive subs out there all seem to be very low in efficiency. You can make this up with numbers, but remember that being located about the room they will add more like 3 dB than 6 dB. So lets say your sub is 85 dB efficient, it would take at least three to be competitive with the Harpers, and then they probably wouldn't have the same MaxSPL - efficiency is not MaxSPL. I would think that three subs >90 dB would be best, two if they are say 94 dB. Never use just one.

When I suggest many smaller subs, I was not thinking about the uber-low efficiency that some of these subs seem to have. That can be a problem.
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Old 18th July 2009, 10:00 PM   #1136
jdubs is offline jdubs  United States
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Thanks Earl. Looking forward to seeing how they turn out (pics, please)!

Also, on your website you mention that the Harper kit has the enclosure assembled. What needs to be done to complete the speakers?

-Jim
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Old 18th July 2009, 10:58 PM   #1137
pjpoes is offline pjpoes  United States
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Many of the inexpensive small subwoofer's out there are trying to achieve very low bass in a very small package by increasing the efficiency at say 25hz at the expense of efficiency at 100hz. It seems to be mostly accomplished through extremely heavy cones and very long excursion. I'd argue that even stuffing the ports on some of the units out there (for ported units) would still not net the type of performance Dr. Geddes was looking for when recommending the multiple bass speakers approach.

I wonder if a clearer recommendation might be to suggest twp bass speakers, which few commercial examples exist for, and a single ultra low bass speaker (I know this is more commensurate with your specific recommendation, but I recall also seeing that it doesn't matter what you use, or that three subs are fine). In other words, I think diying is the best bet for those low bass speaker setups. I'd bet that a few 8" or 10" pro-bass drivers in sealed enclosures, which could offer 94db's of sensitivity and probably handle no more than 150 watts and be doing just fine. In fact', since the recommendation is for two, I'd suggest getting a single amp rated at 2-300 watts, which is optimized for 4 ohm loads anyway, and drive both woofers off that amp, which would net the 4 ohm load.

I had three subs which would be better classified as ULF instead of what I needed, which was more of a bass augmentation speaker. The drivers in two of them were the Dayton RS 12" SQ subs, which have good upper bass extension, so I thought would work great. However I was having a lot of trouble fixing some issues in the upper bass range, and upon closer measurements of those speakers at close range, I found they were more rolled off above 80hz than I had realized. I switched those drivers out with 12" B&C drivers and sure enough the response switched quite drastically to having less of the ultra low stuff, but more efficiency and a flatter response in the upper area of it's usable range. This seemed to improve consistency and smoothness in the room as well. The difference in measurements are relatively small, but I seemed to have a bit of phase cancellation at one part of the range when the subs where in correct acoustic phase in another part. I also had somewhat of a response hole between 70hz and 150hz, with an over-abundance of bass below that point. This seemed to help deal with that problem. The 12" B&C drivers were picked up as recones from a local craigslist add, and are less than ideal long term solutions, but I plan on changing to the bandpass option Dr. Geddes is offering in the future anyway.

Point of this long post is that as I continue to fiddle with my bass response, i find that the closer I get to Dr. Geddes own setup and specific recommendations, the better things are. Initially I had found a pretty sizable improvement in the response just utilizing multiple subs in various parts of the room. However problems still existed, and while it fixed some, it also seemed to create some minor ones. I found that three true subwoofers with response optimized for bass down into the 20-30hz range are less than ideal for this application.
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Old 19th July 2009, 03:52 PM   #1138
gedlee is offline gedlee  United States
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Quote:
Originally posted by jdubs

Also, on your website you mention that the Harper kit has the enclosure assembled. What needs to be done to complete the speakers?

-Jim
Install the drivers, wire the crossover and paint. No woodworking involved.
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Old 19th July 2009, 04:06 PM   #1139
gedlee is offline gedlee  United States
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Quote:
Originally posted by pjpoes
It seems to be mostly accomplished through extremely heavy cones and very long excursion.
Matt Thats quite true. From an advertising point of view, they can say "28 Hz LF response" and "large excursion capability", both things that ring to the novice as "good". They just forget to note that an 85 dB senitivity makes them pretty useless unless you buy a half dozen of them.
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Old 19th July 2009, 04:20 PM   #1140
jdubs is offline jdubs  United States
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Quote:
Originally posted by gedlee


Install the drivers, wire the crossover and paint. No woodworking involved.
So, the wave guide is already installed? Do you have any pictures of what the cabinets for this kit look like?

Thanks,
Jim
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