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greetings: i am newly active here (spending more time on AA now that A-gon is a mess). its great to be here. i know that there are various threads over the years touching on this subject, but i am looking for suggestions regarding good cabinet designs for 15 inch "co-axial" speakers. i just picked up some university 315s, but might be interested in trying altec 604, tannoys, EVs, great plains, etc. in the future to compare.
i use 2A3 and 45 SET amps, so need to maximize efficiency. i like healthy bass response. listen to acoustic jazz as well as heavy rock.
my listening room is medium size (perhaps 14x18 with 9 foot ceilings, rectangular but not a perfect rectangle). because of house features and furniture placement, the speakers can not be in the corners, but need to be about 1/3 of the way out into the room and a bit in from the walls.
prefer relatively narrow width, can go moderate to deep in depth, and can go tall. its on the 2nd story, so manageable weight is also a plus.
i would appreciate any suggestions, tips or experiences that you care to share.
thanks -andre
PS i am in chicago, if anyone in the area has appropriate cabs they are not using.
-andre d
Follow Ups:
You might find something amongst the Tannoy cabinet designs that would work for you. Perhaps the rectangular GRF?
ray
thanks much. it appears to my untrianed eye that the GRF is a "horn" design?
what are the pros and cons of a large front opening like that in a box of this size as compared to ports in back? esp. as relates to bass response.
-andre
-andre d
It's a horn design. I'm not qualified to answer your second question.
ray
Too bad you can't use the corners. A 15" coaxial driver in a Jensen Imperial corner horn is an awesome combination.
Here is one Jeffrey had made:
I found parameters for the woofer that (I think) is the base of the 315 coaxial (see link). Looks good, a very light cone for a 15.
With a coaxial, you design the box for the woofer as usual (in terms of internal volume, porting etc). Your only limitations is that you have to put the coax centre higher up than you'd normally put a 15" driver. This is adds to the challenge of getting as much bass as possible out of a light driver with a fairly high Fs.
For a simple box that you can try multiple drivers in: a ported tower, slightly oversized. Make it a bit too big so you can modify internal volume as you swap drivers. Mount the port(s) in a removable plate so that you can swap them around too. You could put this plate on the back of the cabinet to hide it. Also, that allows you to be lazy and run cabling in through the port.
Alternatively, go with something modular - a fairly small sealed or aperiodic box for the coaxial, and a bass bin that goes up to 100Hz or wherever, and that acts as a stand for the coaxial. This'd go a little lower, be easier to get up stairs, probably sound better, but obviously have a higher cost / parts requirement.
Those measurements look a little strange to me. Re(series) should be about four times Re(parallel), and such is not the case. Also, there should not be so much change in Qes. My guess is that some error was made in the parallel-coil measurements.
Anyway, I think the series data is good, and a little 2A3 amp will want to see the coils in series.
The key to getting good bass out of this woofer is BOUNDARY REINFORCEMENT. Left to its own devices, it is very weak below 100 Hz. If you can put 'em in room corners, I would try maybe 4 cubic feet tuned to 40 to 45 Hz as a starting point. If no corners are available, tune to 50-55 Hz and have the speaker down near the floor, angled back a bit. If you want the speakers up near ear level, go with 2.5 cubic feet tuned to 80 Hz, and add a subwoofer for 80 Hz on down.
My advice is free and worth every penny.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
thanks. if you or anyone have good links on info on how to tune a cabinet for certain frequencies, i would appreciate seeing those.
regards -andre
-andre d
thanks holllowboy! the modular idea is one that's new to me, and has a lot of appeal. any idea where to look for successful designs for such?
i have never built or designed a speaker cabinet and am looking to stand on the shoulders of giants as much as possible.
-andre d
By 'modular' I just mean to have the bass and mains seperate. Lots of bookshelf + sub systems are made this way. In high efficiency, there's all the horn+bass box systems based on the Oris and Azura, OB+bass box systems based on the PR170MO, and many more. You can look these up in this forum.
It is difficult to get a coaxial's woofer to go flat from where it crosses over (about 1.5-2KHz?) right down to 50Hz or so. As well as the driver specifications (light cone, extreme midband sensitivity etc), your stated unavailability of corners, the (I'm guessing) requirement to position the driver near ear height, and upstairs room (timber floor?) all add to this.
Duke's take on going modular is two tops, 1 bottom:
go with 2.5 cubic feet tuned to 80 Hz, and add a subwoofer for 80 Hz on down*
My take on going modular is two tops, 2 bottoms:
~1 cubic foot sealed / aperiodic, and add one subwoofer for each channel, from ~140Hz on down. Use the subs as stands for the coaxials.**
*for a bulky driver like this, the smallest internal width and depth you can have is about 40*30cm (16*12"), which, assuming the driver, port and bracing take up half a cubic foot, sets the height at about 70cm (28").
This is not really tall enough for a floorstander. I'd recommend purposely building such a cabinet oversized - make it taller to bring the driver to ear height - then fill some of it back in. This avoids the need for stands and gives you flexibility to remove the fill later to try other drivers / positions / tunings.
**I made what became my bedroom system with 15" coaxials, and reinforced the bass with additional 15" drivers in the same box. Even then, they are still a bit bass shy, hence my enthusiasm for subwoofer augmentation.
thanks. any info on how to "tune" a cab for certain frequencies would be appreciated. -andre
-andre d
Probably best to grab some free software and play.
I like hornresp. It was written to model horns, but can also do sealed and ported boxes. There might be something simpler out there: google away and see.
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