AndrewT said:
Thank you Andrew. This I already know. That is how I got 134.81 inches as one dimension given. The other two numbers listed converted to 21.19 inches each. That means nothing to me because from the photos it is clearly not the internal dimensions of the rectangular pathway, or anything else that I can see in the pictures.
Pinkmouse said he got all of this out of a single sheet of MDF. Well then the woofer sure as heck cannot be much larger than a 10 incher now can it?!
I am unable to work in metric values with speaker cabinet construction. I am getting old, my brain is foggy and I suffer from severe chronic pain. My request for inch measurements is basic and simple. Please humor an old fool who is keenly interested in the subject matter.
pinkmouse said:
How can I not comply with that request?
Overall pipe length is 152", with the tap at 21.3", pipe C/S area is 54.6 square inches, and the driver is the Kef B139.
Al,
Thank you for the information. Aha, the Kef is not a circular woofer! That explains the truncated hole cutout which I had actually thought was there for acoustical LP filter purposes.
Care to share cabinet OD dimensions, distance between dividers? Sorry for so many questions. Pretend I am trying to make a construction diagram to copy your fine work for myself and am looking for any info that I would need to do so to mimic your effort accurately. For example, giving me simply cross sectional area of the pipe does not define either side dimension.
I even have a router which will shoot sparks when I attempt to use it to copy your work. Is that getting close enough?
Oh, BTW, you did remember to install the driver and a wire to it before you closed it all up tight.
pinkmouse said:Once the design is proven, I will post proper drawings.
Oops!
OK, please forgive my inquisition. I am merely trying to make mental models, in perspective of the projects that have been documented here in an effort to figure out something to build and experiment with myself that has a high degree of probability for satisfaction with minimal waste.
Is it your intent to use this set flat as a coffee table type sub? That concept is one that would be quite practical in my living room setup.
I have a pair of 12 inch Hollywood 1280-D 400W RMS car type subwoofer drivers (2X 4 ohm VC`s each) that have plenty of excursion and large magnets that I think could be OK for a HT sub. They suffer foam surrounds but I got them for free so in this case I am willing to break my very strict `NO FOAM` speakers rule which is technically that I refuse to spend precious money on foam surround speakers. These bare drivers incredibly survived sitting outside exposed in the rain and snow for a month or more in a scrapyard. They needed some TLC and a dab of goop to repair a tear in one roll surround but I think I have them in useable condition with no cone rub noises now.
rcavictim said:
No, I was going to put them upright in the two front corners of my room, but they would work in that configuration.
As for your drivers in these boxes, I don't think that would work, THs are very sensitive to driver parameters. If you can measure yours, and ask GM nicely, I'm sure he'd simulate them for you.
AndrewT said:
Greets!
I don't have the aversion to an access panel that you apparently do, but if you consider a rising response an acceptable trade-off (I do since it's better damped, but this thread seems to be 'max flat' centric) you can shift the driver position to the extreme end for easy access through the mouth, making the layout:
L12 = ~92.39 cm
L23 = ~342.42 cm
L34 = ~15.24 cm
GM
Attachments
I have no problem with a slight rising response, but it's too late now!
Well, I had to stop for the night as there are very young children next door who are easily disturbed, so no more progress tonight. All I have left to do is put in the mounting plate for the access panel and wire it up, so I might get it fired up tomorrow before I have to go out.
Well, I had to stop for the night as there are very young children next door who are easily disturbed, so no more progress tonight. All I have left to do is put in the mounting plate for the access panel and wire it up, so I might get it fired up tomorrow before I have to go out.
GM said:
GM,
That looks exactly like my drivers except mine have a slightly different style removable rubber cover on the stacked magnet assembly. Xmax one way spec sounds about right. I can confirm Fs as that is a simple test but do not know how to measure TS parameters yet myself.
What is your opinion of trying to make a stacked horn sub for a single or pair of these? Only want one cabinet if possible, coffee table style folded box would fit in well here. 10-15 Hz to 50 Hz should be good fill below my FR stereo mains that actually do go to 20 and I can hear at 30-35 Hz but don`t shake the room at the flea tube power I run.
I worry the published Fs (24.3 Hz) may be too low to use in a TH. Is this model driver used as a pair better suited for a labhorn type enclosure?
rcavictim said:
Greets!
At a glance, with a fairly high Vas, high Qts combined with a max gain BW of only ~10.75 - 54.92 Hz we're looking at a large 'one note' boombox if either a tapped pipe or conic horn and when I shift 'Fl' up to 14 Hz I wind up with ~122 dB from ~18-50 Hz if a 14 Hz expo flare is used, but it's a whopping ~345.3 ft^3! Using two drivers in clamshell isobaric will cut this to ~86.32 ft^3 and have a similar output due to doubling the Xmax, but still an unacceptably large cab, so until I can look at TLs, I've got nothing for you.
GM
GM said:
GM,
Hmmm, one note boombox, pretty much the definition of a car subwoofer system no doubt, the application for which these drivers were clearly made.
Thanx for taking the effort to examine their suitability in a tapped horn (sorry I had a flash of mentalpause when I typed `stacked horn`), and also in a expo/conical horn. You are right about the cabinet being unacceptably large.
Shortly after fixing these and drying them out I duct taped one into the end of a 12 inch sonotube and had a second nesting section that could be used as a trombone element. This assembly was lain on the living room carpet and testing pursued with audio sine wave gen and low power (40 watts/ch RMS) SS amp. Each voice coil got a 40 watt channel to drive it. What I got was definitely not a `one note bass` wonder but it seemed the open ports were totally in the wrong places to properly excite the room. I did get a lot of the usual shaking and rattling however. I tried open ended and closed ended line with different tuning lengths up to about 17 feet IIRC.
There may be something there for these drivers in a traditional folded TL or pipe cabinet, with or without taper. I suspect they should be used mounted with the cone facing horizontally. Left sitting on their backs the cone has sunk a lot into the magnet structure,
Happy New Year and all that jive!
Well, when all else fails, a TL will usually get the job done, though to keep the size semi-reasonable with this driver means it has to be Isobaric. Assuming a 200" long square tube just big enough to mount a driver (~12.5" square) = ~13.92 ft^3 or < 4 ft^2 before factoring in all the divider thicknesses and the extension to house the clamshelled driver. 1 W shown and with Isobaric you have 2x the excursion, so should pound pretty good and once the ripple is XO'd down will have a very good transient response:
GM
Well, when all else fails, a TL will usually get the job done, though to keep the size semi-reasonable with this driver means it has to be Isobaric. Assuming a 200" long square tube just big enough to mount a driver (~12.5" square) = ~13.92 ft^3 or < 4 ft^2 before factoring in all the divider thicknesses and the extension to house the clamshelled driver. 1 W shown and with Isobaric you have 2x the excursion, so should pound pretty good and once the ripple is XO'd down will have a very good transient response:
GM
