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Old 15th August 2010, 01:31 AM   #1
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Default A project of Nathan or Abbey and subwoofers

Hello

I'm trying to decide between a pair of Abbeys or a pair of Nathans. I finally got the polar map plotting program working. Abbey seems to have much better directivity than Nathan.

A while ago I downloaded the datasheets for the mid/bass drivers of both.

Nathan has B&C 10PS26, datasheet at http://www.bcspeakers.com/PDF/PRD/10PS26.pdf
Abbey has B&C 12TBX100, datasheet at http://www.bcspeakers.com/PDF/PRD/12TBX100.pdf

I see that 10PS26 goes up to 2kHz with no problems. Above that is the first breakup mode. 12TBX100 is problem-free up to 1kHz if one wants to avoid the breakup region. I haven't seen the crossover frequency specified anywhere, but someone estimated it at 1.2kHz. Can this be a problem in any situation? Has anyone ever heard anything odd caused by this?

A question for everyone who has built an Abbey for themselves. Has the on-axis dip been a problem (at all)? Can you hear it, and if you can, in what kind of situations does this happen?

I also saw in the plotting program that Abbey goes up to 16kHz, Nathan up to 18kHz. Is everyone sure that they will never miss the frequencies above that? As far as I remember, some people have been able to spot a difference between a 44.1kHz and a 96kHz digital source in an ABX setting. Sorry, I have no reference for this. But if true, does that say anything for speakers able to reproduce frequencies above 18kHz or 20kHz?

Bottom line is that is there anything that you can say for Nathan that you can not say for Abbey, in addition to the smaller footprint, i.e. floor space?

My second question is about subwoofers for use with Nathan or Abbey.

I plan to build four small subwoofers and locate them pseudo-randomly in my small living room. I heard that it is recommended to use many subwoofers in the 40-80Hz region and just one or two for 20-40Hz. Is there any problem if I build four, all for 20-80Hz?

Whether they be sealed, ported, bandpass or with a passive radiator, is to be determined. Any recommendations are welcome. Four Seas L26ROY drivers in sealed boxes would be overkill or just right?

Not sure if this is the right place to post this, so all moderators, feel free to move it to a better place.

Last edited by Thinkcat; 15th August 2010 at 01:34 AM.
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Old 15th August 2010, 06:05 AM   #2
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You can see in Dr. Geddes's plots that he has avoided break up troubles in all his speakers. Beyond that I'm no help.

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Old 15th August 2010, 11:53 PM   #3
Pallas is offline Pallas  Pakistan
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IMO, if you can afford the bigger ones and fit them into your space, buy those. If nothing else, they'll give you better bass and less dynamic compression.

As for your sub plan, I'm sure it'll work fine, though I would do something different. The Seas drivers, I think, are better suited to vented enclosures than sealed ones, and IMO multisub systems with a bunch of fourth-order rolloffs on the bottom are a pain to get right. Then again, they may work well bandpass. I've not modeled them.

Still, at those prices I think getting Dr. Geddes' subs would be more efficient. They're really quite the bargain, especially when you consider the value-added from the EQ settings he provides based on your room measurements. Alternately, the Peerless XXLS and Dayton Reference are very high quality, lower cost drivers.

Personally, I prefer at least one larger sub, in a corner. What I do - I use 12" Tannoy Dual Concentrics rather than Dr. Geddes' speakers up top, but the principles are the same - is use one larger (15") sub and three other smaller ones (2 x 12" on the floor, 1x 10" up high). But others run identical subs in all positions, and both approaches work fine if you can get enough SPL and have the EQ and measurement equipment needed to get everything working together.

Depending on the subwoofer drivers, you can run them all full bandwidth, or not. Measurements should be your guide there.
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Old 16th August 2010, 11:21 PM   #4
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I built a pair of Abbeys, and I have to say they sound terrific - with no off-axis irregularities at all - as far as I can detect. The measured frequency response is basically flat from 20 to ~12 kHz with the speakers toed in ~45 degrees and with two 20-125 Hz bandpass subs mixed in appropriately. Personally, I wouldn't give a second thought to anything beyond ~12 kHz, since my 50+ year old ears can't really hear anything that high anyway. In terms of imaging and dynamics, all the action is in the 1-8 kHz range anyway.

I was initially concerned about the size of the Abbeys, but that has never been a problem, for me or my wife (YMMV, though). I have not heard the Nathans, but I will say that the mid-bass response of the TBX100s is truly wonderful.

So all in all, I have to say I have been very happy with Earl's speakers. I don't think you will have any problems at all with 4 subs - no matter what particular kind you end up with.
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Old 18th August 2010, 11:08 PM   #5
pjpoes is offline pjpoes  United States
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I have abbey's and Abbey measurements in room. In room measurements always roll off at the higher frequencies because of the room absorption. My speakers are flat to 18khz and roll off, they are Abbey's. The roll off beyond that point isn't brickwall either, so there is extension beyond 18khz, though not a lot.
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Old 18th August 2010, 11:11 PM   #6
pjpoes is offline pjpoes  United States
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Yeah I know, the impulse response is bad, the response is a bit messy, but the general shape is right I think.
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Old 22nd August 2010, 05:40 AM   #7
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That's an awesome in room response!!!!!!

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Old 22nd August 2010, 10:43 AM   #8
jzagaja is offline jzagaja  Poland
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pjpoes - why do you have a dip at 1kHz?
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Old 22nd August 2010, 09:30 PM   #9
pjpoes is offline pjpoes  United States
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Wish I knew, I've seen it in other manufactured horn speakers, maybe its a horn thing. Maybe its my room? Maybe I did something wrong when assembling the crossovers. I have no real idea. Dr. Geddes doesn't show that in his measurements, so I'm not really sure.

It's in room with lots of things that could mess up the response, so it may be nothing more than that. I mean, as Dr. Geddes pointed out before, look at that impulse response, not very clean.

The measurement was a single point measurement taken at the listening position with a lot of crap still in the room from my unpacking. I took it for getting the bass setup. It was minus any Bass EQ devices other than the 1 bang PEQ's in the sub amps themselves, and even those weren't necessarily optimized. I was trying to figure out the best setting to measure the bass accurately for making proper adjustments and balance. I've not taken new measurements since then so I have nothing better to show.

The top end response is good because of the speaker design. The rest isn't great, I'd cal that a mess. The bass needs a lot of work. I'd say its ten fold better since I moved the subwoofers around, but I've still not gotten the crossover points quite right, I have virtually no LF dampening in the room, just a lot of things that aren't helping there. The upper response looks good, but its a really reflective room. I have hardwood floors, solid walls, no curtains, and even the dimensions are less than ideal. The room is 15'x14'x8'.

I have hung up my 4" and 6" acoustic panels today, so that should help, and I should take new measurements. I still have bare floors. I didn't want to cover those great floors completely, but I wanted a rug that could span the width of the speakers, and that meant a 13' wide rug. Those are hard to walk into a store and buy, so I had to order it, and its a 6 week lead time. Hopefully the carpet, the pad I"m putting under it, the new panels should combine to improve things. Maybe that dip will go away too? Who knows.
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Old 22nd August 2010, 09:38 PM   #10
jzagaja is offline jzagaja  Poland
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If your crossover is 1st HP and 2nd LP then the coil in LP is too large or polarity. Your room looked quite empty. I'm asking myself use or not multiple subs in 16 square meters - typical room in a hotel. If you weren't happy with electronic EQ then what to do - maybe sealed sub with a shelving filter?
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