fb said:
You're welcome!
Of course! It's what smooths out the TH's response and limits its HF BW. You can see its effect on the SPL, impedance, and impulse plots.
Right, true, but you asked what the deal was with inductors, so this is all part & parcel of it whether or not it's applicable to LF BW apps........
GM
fb said:Now can someone please tell me what the deal is with inductors? This box needs a roughly 5mH inductor in series.
What are the downsides to using a design with added inductance? Reduced power handling?
Would the 500WRMS Erse Inductors at Parts Express be alright for the 600W amp I plan to use?
Ta
The problem with most high-power ferrite/metal core inductors is that they're not really linear, they start to saturate at high currents.
The only sure way round this is to use big air core inductors, but these are pretty expensive for subs because you need high inductance and low series resistance to avoid power loss.
If you mean the Erse 14g air core inductors like these
http://www.parts-express.com/erse-14-gauge-air-core-inductors.cfm
then these are very good so long as the resistance isn't too high (which depends on what value you need) -- the 12g ones are lower resistance, and are 50% off at Erse at the moment
http://www.erseaudio.com/Products/XQCoils12Gauge
Ian
This is going to sound incredibly dumb, but it's something I've wondered for a long time.
If you wire two speakers in series, wouldn't the first speaker act like an inductor for *second* speaker?
I mean, a speaker has inductance right? The voice coil acts as an inductor.
Due to that, wouldn't the series inductance completely alter the thiele-small parameters for the other speaker? The inductance and series resistance should raise QTS for the other one, shouldn't it?
If you wire two speakers in series, wouldn't the first speaker act like an inductor for *second* speaker?
I mean, a speaker has inductance right? The voice coil acts as an inductor.
Due to that, wouldn't the series inductance completely alter the thiele-small parameters for the other speaker? The inductance and series resistance should raise QTS for the other one, shouldn't it?
Speakers in Series
This may have the information you are looking for:
http://www.cartchunk.org/audiotopics/SeriesSpeaker.pdf
Regards,
This may have the information you are looking for:
http://www.cartchunk.org/audiotopics/SeriesSpeaker.pdf
Regards,
Sorry, you can't have it both ways. You're right in that the driver's Le value doesn't change any more than its Qts, so this is true in both cases, not just in parallel, but unlike Qts, their effective values do.
Edit: "...... the effective Le doubles with two drivers in series and halves if in parallel.......".
GM
Edit: "...... the effective Le doubles with two drivers in series and halves if in parallel.......".
GM
GM said:
By definition inductance is the amount of voltage dropped across an inductor for a given rate of current change through it. Since power amplifiers are voltage sources, the voltage across each inductor remains the same for parallel inductances. The current through each inductor is the same as if were alone. The power amplifiers just supplies more current for the parallel load. Therefore, their effective inductance does not change where they are paralleled. The only times this would not be true is if the inductors share a common core; i.e. common core feedback and if you happen to own one of Nelson Pass' current source amplifiers. Since the loudspeakers don’t share the same pole piece, it is impossible for the effective inductance to be less than a lone single inductor.
First set of measurements posted.
These are for the core of the unit. The rest is easy.
Warning... the two 4.5" ramps are NOT 45 degrees.
I'll add more as I go and I have a ton of build pics as well to process. I'll post a skp file as well later.
I'm not too crazy about sketchup.
This is a RAW working version. Don't flame me for not dadoing and beveling every edge, or cryogenically freezing the wood before cutting with a diamond blade. Frankly, much to my surprise I couldn't hear any difference between a one of these and the second version with all the "properly" smoothed surfaces. Since I wound up going into "combat" before they were done, I had to go with the basic version. They Work...period.
Maybe you guys can polish them a little.
Same place
http://www.screamersusa.com/furybox.html
These are for the core of the unit. The rest is easy.
Warning... the two 4.5" ramps are NOT 45 degrees.
I'll add more as I go and I have a ton of build pics as well to process. I'll post a skp file as well later.
I'm not too crazy about sketchup.
This is a RAW working version. Don't flame me for not dadoing and beveling every edge, or cryogenically freezing the wood before cutting with a diamond blade. Frankly, much to my surprise I couldn't hear any difference between a one of these and the second version with all the "properly" smoothed surfaces. Since I wound up going into "combat" before they were done, I had to go with the basic version. They Work...period.
Maybe you guys can polish them a little.
Same place
http://www.screamersusa.com/furybox.html
FURYBOX POSTED
Everything you need to whip one up is on the page.
The cabs use 21" wide boards.
The two 4.75" reflectors will require a 12 degree angle cut into one side of them to seat the easiest.
The reflectors are more important to break up the corners than actually reflect the sound.
Cheers for now, won't be able to post step by step pics untill next week.
http://www.screamersusa.com/furybox.htmlhttp://www.screamersusa.com/furybox.html
Everything you need to whip one up is on the page.
The cabs use 21" wide boards.
The two 4.75" reflectors will require a 12 degree angle cut into one side of them to seat the easiest.
The reflectors are more important to break up the corners than actually reflect the sound.
Cheers for now, won't be able to post step by step pics untill next week.
http://www.screamersusa.com/furybox.htmlhttp://www.screamersusa.com/furybox.html
"do not use solid rear brace, or low frequency will suffer"
Now there's one of those things a person doesn't think about everyday... And if it hadn't been built / tested that way, no one would ever guess that.
Makes me wonder how many of my test boxes would have different response with different bracing.....
Now there's one of those things a person doesn't think about everyday... And if it hadn't been built / tested that way, no one would ever guess that.
Makes me wonder how many of my test boxes would have different response with different bracing.....
The test cabinet had no bracing at all. 102-103db at 40hz.
The first real build had lost quite a few db at 40. I had no choice but to keep building. On the other 3 cabs It dawned on me that I forgot to compensate for the bracing volume. So I pulled a BFM and just cut out as much as I could safely get away with.
Most of the 40hz returned. Just leave about 1.5inches around
the edge of the brace as shown and round the corners. Don't try to cut sharp pretty angles because they only weaken the brace.
It's there for structural integrety not asthetics.
Luckilly I had discovered that with birch I only needed that one 90 degree brace in front which is one of the scrap parts cut off the side for the wheel well on the first box so I don't have to fix that.
I just got a dremel Multimate last week so I will be able to reach up into the first box and cut holes in the brace.
The original cth15 sounded great and it had the brace tapered
as a central spine inside the cabinet. It was just too darn hard to duplicate a second time and it needed to be longer.
BE liberal with the glue. Use polyurethane as it expands.
The bottom panel for the wheels should be 22.5 inches wide
so that the screws will go in from the bottom. This also puts the weight and stress on the wood and not the joint itself when rolling across that parking lot they never repaved.
Certain big name expensive cabinets fall apart at the wheel panels because they are screwed in from the side.
The first real build had lost quite a few db at 40. I had no choice but to keep building. On the other 3 cabs It dawned on me that I forgot to compensate for the bracing volume. So I pulled a BFM and just cut out as much as I could safely get away with.
Most of the 40hz returned. Just leave about 1.5inches around
the edge of the brace as shown and round the corners. Don't try to cut sharp pretty angles because they only weaken the brace.
It's there for structural integrety not asthetics.
Luckilly I had discovered that with birch I only needed that one 90 degree brace in front which is one of the scrap parts cut off the side for the wheel well on the first box so I don't have to fix that.
I just got a dremel Multimate last week so I will be able to reach up into the first box and cut holes in the brace.
The original cth15 sounded great and it had the brace tapered
as a central spine inside the cabinet. It was just too darn hard to duplicate a second time and it needed to be longer.
BE liberal with the glue. Use polyurethane as it expands.
The bottom panel for the wheels should be 22.5 inches wide
so that the screws will go in from the bottom. This also puts the weight and stress on the wood and not the joint itself when rolling across that parking lot they never repaved.
Certain big name expensive cabinets fall apart at the wheel panels because they are screwed in from the side.
I apologise to all as I cannot make a nice pretty PDF and I have not had time to learn autocad. I'm still quite slammed at the moment. I am sure we'll all be reverse engineering this thing and tweaking it for awhile anyway. We can worry about a nice presentation when it's been beat on for awhile.
I'll just keep adding to the sitepages as I can for now.
Cheers
While this is the best practical DIY cab I could come up with, the CTH did sound much nicer in the upper ranges. Most of the test boxes with the most complex tapering schemes requiring lots of intricate little angled pieces, seemed to sound the smoothest. I guess that's what Danley means by "Lots of wood". To me getting a TH to sound great below 90hz is the easy part, it's getting it to smoothly transition up to 125hz+ while still hitting below 40hz , without phase problems, that's the hard part.
Then again, that's why this thread is here. 
I'll just keep adding to the sitepages as I can for now.
Cheers
While this is the best practical DIY cab I could come up with, the CTH did sound much nicer in the upper ranges. Most of the test boxes with the most complex tapering schemes requiring lots of intricate little angled pieces, seemed to sound the smoothest. I guess that's what Danley means by "Lots of wood". To me getting a TH to sound great below 90hz is the easy part, it's getting it to smoothly transition up to 125hz+ while still hitting below 40hz , without phase problems, that's the hard part.
Then again, that's why this thread is here.
JB, this box has higher compression than yours and I suspect your low end is a tad better at moderate levels. I think this one may actually go louder than the big one with less chance of driver damage at constant high levels. The furybox is a "beat the hell out of it" transportable compromise. We've certainly beat up on 4 of them pretty well and watched direct radiators running in parallel with them physically disentegrate.
There's also apparently a guy running around Orlando with 8 36x36 versions ,probably based on your box, that are working well, outrun his old cerwinvegas, but don't do well below 50hz. Maybe he'll chime in here sometime.
Nice thing about the wheel support having the cabinet sides on top, is if the box gets messed up around the wheel area, it's pretty easy to replace the whole panel or repair it. Not so with the Meyer boxes I recently had to repair for a friend. Good idea for any live box.
There's also apparently a guy running around Orlando with 8 36x36 versions ,probably based on your box, that are working well, outrun his old cerwinvegas, but don't do well below 50hz. Maybe he'll chime in here sometime.
Nice thing about the wheel support having the cabinet sides on top, is if the box gets messed up around the wheel area, it's pretty easy to replace the whole panel or repair it. Not so with the Meyer boxes I recently had to repair for a friend. Good idea for any live box.
iand said:
Thanks Ian. The Erse XQ 12g look great - though they are a bit expensive even when on special... I emailed Erse, and they suggested that their SuperQ 14G would offer nearly the same distortion performance with my amp RMS rating of 600W. They have a video showing THD vs. input power... Do you think this is a reasonable proposition?
Cheers
Sorry to double post this, but does anyone think it's worth my building?
My target is ~30hz -> ~100hz, 2pi space, ~126dB. It's pretty close, and I like that it's done with a single driver (cheaper), and within linear Xmax. I've no doubt I could do a bit better using 2 drivers for the same SPL, but at double the cost.
Thanks
My target is ~30hz -> ~100hz, 2pi space, ~126dB. It's pretty close, and I like that it's done with a single driver (cheaper), and within linear Xmax. I've no doubt I could do a bit better using 2 drivers for the same SPL, but at double the cost.
Thanks
Attachments
fb said:
Thanks Ian. The Erse XQ 12g look great - though they are a bit expensive even when on special... I emailed Erse, and they suggested that their SuperQ 14G would offer nearly the same distortion performance with my amp RMS rating of 600W. They have a video showing THD vs. input power... Do you think this is a reasonable proposition?
Cheers
Yes, the biggest SuperQ inductors should be fine at these power levels and are cheaper/lighter/smaller -- at least if Erse show distortion levesl this is far more than most suppliers do.
For 2kW/4ohms and above only the XQ 12g will do...
Ian