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A project of Nathan or Abbey and subwoofers

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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.
 
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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.
 
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.
 
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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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.
 
The HP isn't truely 1st order, it has notch filters that steepen the response. The LP is 2nd order, but the Inductor is what Dr. Geddes specs. The dip isn't enough to be polarity, plus I tried switching it once, doesn't make it go away. I should check again and make sure its right, but the Tweeter is supposed to have inverse polarity to the woofer, and I believe that is the case, as its supposed to be.

I tried playing around with the LP filter myself once since I found the inductors to be out of spec slightly anyway. They were supposed to be 3mh and were emasuring 3.2mh. I unwound them until I measured 3mh and tried again. Then unwound them to 2.9mh, but didn't want to go lower than that, since once you undo it, its hard to get the winds back just as tight. I also tried a different Inductor I had that was 2.5mh, but that creates a problem at both 1.5khz and the 800hz area where there is a bit of a bump right now.

Dr. Geddes redesigned the crossover and I've asked about the schematic so I can try it, but he seems quite insistent I shouldn't bother. I'd guess that the upgrade makes a bigger difference than the same kind of money spent on other sorts of tweaks people do, but he seems to feel its a waste of money, or at least thats my impression. If he doesn't feel that way, Then PLEASE send me the schematic.
 
Whats your polar response look like with each of those though? You can't just look at a dip at one point based on a simulation. Like I said, when I lowered the coil size, I found the response change to be problematic, and to add to that, I saw signs that the polar response was no longer smoothly transitioning into the horn, so I stopped messing with it. Basically, I'm going to trust that Dr. Geddes knew what he was doing when he designed it. If I have to live with a small dip of at worse -5db's at 1khz (that may or may not be a speaker response issue) to ensure a flat polar response, I will do so.

I again would caution you to comapring a simulated crossover response change to the inroom measurements. These aren't quasi-anechoic, they aren't the measurements you would use in crossover design, they are quickly taken in room measurements at a listening position 4 meters away.
 
I understand your point, I'm just reluctant to make crossover changes based on in room measurements. Too many factors could be causing the problems. Again, you also have to consider the power response, the entire response across the polar area. If making changes fixes the response in one area but messes it up in others, you have to consider if that makes sense. Weight it against the effect of say a 3-5db dip at 1khz.

I looked at some other measurements I have from my last house, from each speaker, different angles, etc. I have no quasi-anechoic ones that are worth considering, the gated measurements are a mess, but basically this is what I found. The 1khz dip is always present, but it varies. The dip seems to be roughly 3-5db's relative to the output at say 500-800hz, but is sometimes as little as 1db relative to the tweeter. I don't believe that changing the crossover will help that unless I change to a 3rd order. The shallower slope of a smaller inductor will cause the 400-500hz range to go up. The Woofer uses a CR in parallel, so its possible that adjusting both the inductor value and resistor value would improve it slightly. If I went into all that, I'd just redo the entire crossover using the new design.
 
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.

I see a small dip in the same region with My Abbeys (~1-1.5 kHz), and it is more pronounced at the prime listening position (exact center) than 2 ft to either side. So, when I average the measurements it is less obvious - but it is still there. I considered the new x-over (which Earl did send me the specs for) but I'm not sure if that would eliminate it. I ended up adding PEQ filter to bring it up a bit (which was easy to do with my receiver). It does make an audible difference because the ear is quite sensitive to small changes at that frequency. If I decide I don't like it in the long run I can always remove it with a few button presses.

Doug
 
Hey Doug, would you mind sending me the new crossover schematic/specs? I work for the University of illinois (illinois.edu) and my service name is "mpoes" that should be enough to get my email. If I still manage to get junk mail after that convolution I might cry.

jzagaja I do know my power response in that Dr. Geddes and myself have measured the polar response of the speaker. I'm a little confused by your comment, my specific point was that when I made certain adjustments I was finding it effected the response. I don't mean a simulation, I mean actual measurements.
 
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