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 on: Today at 08:43:02 pm 
Started by drew gandy - Last post by drew gandy
Updated - Aug 19 2018 - more items added to

I've got bins of little parts (and some bigger stuff) that I really need to part with.  Pictures of sets of bins are at this site.  I would like to just sell entire bin cabinets to someone who repairs stuff. 
I have a shelf of Fender transformers, most of which have been photo'd and listed.  I also have some older speakers.  Some tubes.  Some keyboard repair stuff like old disks from 90s keyboards.  Quite a bit of stuff needs pictures but look through what I have and ask questions if you're interested.

 on: Today at 08:35:18 pm 
Started by drew gandy - Last post by drew gandy
F150 getting 35mpg? Down hill maybe?

But do you drive your F150 at 50 MPH or 70MPH?  It does seem like that graph is optimistic but also consider that to get to 50 or 60 or 70, you have to pass through 10, 20 and 30.  Which brings us to
Personally, my biggest gripe is traffic lights. Ya know, those things that sprout up everywhere and creat traffic. My mpg goes down dramatically when encountering cattle gates, those sets of lights that have you stop every quarter mile for miles. My new truck can (does) show average mpg all the time so I see the effects of traffic.

Yes, the US is vast and many people cover a lot of miles but starting and stopping could be the bigger problem.  I'm curious if there are any studies showing the amount of fuel wasted when drivers stop for pedestrians in busy cities.  I've found it can take 5 minutes to simply go around the block in Streeterville because of all the beautiful people walking.  I use up my gas just running my air conditioner waiting for them.   

 on: Today at 08:21:28 pm 
Started by Nathan Riddle - Last post by drew gandy
I'm puzzled about the missing bug screens.  Seems like an odd thing to remove or disappear.  Is it common, down there in Florida, for the screens to simply rust away in that soup you guys call "air"?  Yes, get the gaps in the comp drivers as clean as possible.  And doing the sweeps is one of the most fun parts of fixing compression drivers.  As Art says, the driver has much more limited output down in the lower mid range but I always found that my ear muscles would react when I had a driver at a level that really made the misalignment buzz well.  Problem is that wearing ear plugs diminishes your ability to hear the 'barmonics'. 

5) I've been reading up on HF protection (seems really necessary as the 16ohm version diaphragm is hard to find/not in production). I can't seem to find a consensus on Zener Diodes vs TVS vs polyfuse vs lights vs fuse, etc.
Appears to be in stock. 

Compression driver protection for these: I have not done any protection for the comp drivers in my TD-x boxes.  But, based on my own mistakes with trying to protect drivers, I would suggest steering clear of anything like a breaker or switch.  You want it to be gradual. 

My second thought was to suspect that your 28v zener voltage is too low.  Just a hunch.  But, the zener concept should cause harmonic distortion when it's doing it's job.  That might be a nice sign to the operator that you're reaching the limit.  The problem might be that it clips higher frequency content (that might have lower actual power) while allowing quite a bit of lower frequency content through.  Because the impedance rises with frequency, the same voltage is producing less thermal rise in the VC at higher frequencies.  And, with actual music, there is likely more sustained tones lower than higher in the spectrum. Couple this with the drooping response with frequency caused by the mass roll off and inductance, and we probably need more voltage at high frequencies (10Khz) than at low (1.5Khz).  That said, this zener protection scheme is more of a transient catch (who unplugged and re-plugged our power?!?) than a long term limiter.  Suffice to say, protection is a complicated thing. 

Since replacement diaphragms are available, I would suggest that you wait until you blow a few and then work up a protection mechanism.  You may not need it at all.  But perhaps someone who has "blown" more diaphragms can chime in.

Looking at your pics, I would be inclined to go through the pcbs carefully and clean up any corrosion while re-soldering every joint.  And probably put some oil on those threaded mounting studs for the drivers. 

6) Any thoughts on where to find this magical TD-'2' xover?
Seems Tom and Drew fussed around with the TD1 after SPL went outta business, I'd love to see/hear what they came up with...,109187.msg1019990.html#msg1019990

A few posts back John Halliburton mentioned TD-2s at Schuba's.  This is a topic that I'd like to get straight.  The way I remember it is that SPL brought in someone to design the "TD-2" after Tom left and that only a few of them were made and installed (was the Cubby Bear supposed to get some as well?).  Conversely, when Tom worked up the new schematic several years ago he called it a "TD-2".  As I recall, he didn't know anything about what they did in the SPL "TD-2" and perhaps didn't want to lend it any credence.  John, please correct me if you can.  But ultimately, I think we need a way to differentiate these things because they are indeed different.  btw, Tom's "TD-2" calls for the BMS 4550 driver. 

As usual, Art's suggestions are spot on.  Well, except I have a bone to pick about one thing.  It's my understanding that the perimeter edge of the midrange entrance holes are best left as square as possible.  The idea is that the cross sectional area of any disturbance in the horn wall is a primary factor in how that aberration will affect the response.  If you round-over the hole edge then you increase the cross sectional area of the aberration. 
I've experimented with hole design for Unity/Synergy entrance holes but most of my play has been on the midrange side of the hole.  I would be delighted if someone has some more info about this.  Art, maybe you have some measurements or info from your travels that conflicts with this?   I would certainly say that "smooth" seems more intuitive for a horn than anything with a sharp edge.  But things aren't always as they seem.

Nathan, I haven't looked at all your measurements yet.  I'll try to do that and perhaps make comments (or just ask dumb questions). 

 on: Today at 07:32:34 pm 
Started by Doug Fowler - Last post by Mark Wilkinson
Hello fellow cheapskates*:

I thought this would be of interest. :)

Advertisements for the Focusrite Scarlett 2i2 Gen 2 claim it to be the best selling audio interface of its type in the world. Given its low price, good looks, massive advertising budget and great specs (except the ones they don't mention), I can see why.

Thx Langston, and in keeping with cheapskate....have you measured the UMC404HD ?   Same price...
I know it at least has much better phase performance ...not to mention 4 ch....

 on: Today at 06:28:02 pm 
Started by Nick Andrews - Last post by Steve Garris
I just use (4) Par 38 cans with flood incandescent bulbs (up to 150w). I had a steel bracket made to mount them on my speakers, and they thread in to the fly points using large thumbscrews. Very cheap, but they work.

 on: Today at 06:18:37 pm 
Started by Mac Kerr - Last post by Mac Kerr
This topic has been moved to LAB Lounge.

 on: Today at 06:12:05 pm 
Started by Dave Guilford - Last post by Paul G. OBrien
Re the Kilomax specs, the biggest difference is that it has a higher Qes which results in the peakier response above tuning around 70Hz and earlier rolloff you see here.

Right, the Kilomax "wants" to be in a much larger box for nominally flat response, WinISD defaults to 23 cu/ft for it initially. If it is crammed into a much smaller box the response goes a bit wonky as David described. Is it usable? Yes certainly but it can only handle about 800w before exceeding xmax because of it's heavy cone and there are better options out there now like the B&C RBX or even the older TBX.

 on: Today at 06:03:56 pm 
Started by Johnathon P. Roof - Last post by Steve Garris
Glad to see this post come up as I ended up giving a local band a help last night with their new DL1608 mixer. I found everything straight forward other than getting the reverb/delay to work.  I scrolled all the way to the right and had the 2 effects faders to 0db or unity.  Went to the channel the singer was singing in and went to the reverb page as an example. Selected a reverb and brought up the fader to the right of the reverb choices and the one one the other side of the reverb settings up as well. No reverb could be heard and no metering seen on them. Same with the delay. Of course the singer was singing so the post fade send should have been there. I only got the mix up and running and left.  Any idea what I may have missed? Not sure if I'll run into one again but it may be handy to know.  A video link somewhere explaining it etc?


Douglas R. Allen

Was the reverb for an aux mix? I had trouble with that, because the fader has to be up on the main mix before any reverb or delay will come through the aux mix. When I say fader, I mean the vocal fader (or whatever you're trying to get effects on). The key to remember is that for any effect, 3 faders have to be moved up.

 on: Today at 05:19:12 pm 
Started by Nathan Riddle - Last post by Nathan Riddle
1) The root problem is "crap in the gap", it just takes a lot of time to get rid of it. It also appears that the driver's bug screens are missing, so if the cabinets were ever set with the horn up, all the crap in the horn would have been funneled in. Some sand and dirt is magnetic.
You should replace the bug screens, nylon netting or nylon hosiery fabric works well.
2)That's the stuff. It can be used on almost anything, last century they used to demonstrate a working CRT TV set completely submerged in an aquarium full of Corrosion X! Trade show electrical inspectors probably put an end to that.. 
It's best to use something like DeOxit and a toothbrush to clean circuit boards before applying Corrosion X, though I've also used Corrosion X to "clean" lots of things.
3) Down at 200-500 Hz, the driver's output is quite low, so the odd harmonics (buzz) generated above are easy to hear. Pink noise (or music) will mask the buzzing.
4) Image courtesy of Mark Seaton ;^). It looks like the throat has already been smoothed, though perhaps could use a "touch up". The mid exit ports are not as critical, though smoothing will reduce diffraction.

1) Nice edit, any dollar store pantyhose will work? Presumably, the thinner leg part will do. Looks easy to mount too as I can place a circle between the metal mount and the rubber seal on the driver.

2) That's...awesome! I have DeOxit I'll spray and pray and clean and when the corrosion gets here hit it with that to help protect. Thanks

3) Makes perfect sense. I'm hoping between cleaning the gap, corrosion, correct VC alignment & cleaning the horn I'll get some better results north of 1k

4) When I think 'smoothing' I think 'rounding' the holes to flare a bit (both entry and exit). Is that correct?


5) I've been reading up on HF protection (seems really necessary as the 16ohm version diaphragm is hard to find/not in production). I can't seem to find a consensus on Zener Diodes vs TVS vs polyfuse vs lights vs fuse, etc.

For live use I'd prefer a 3dB compression instead of simply turning off.

I'm thinking this:
TE Connectivity Raychem RXEF110 1.10A Polyswitch Speaker Protector
With resistor (say 5ohms 50w) in parallel (drop spl by ~3dB, not just turn off)

Or Ivan's method:,138477.msg1289035.html#msg1289035,109187.msg1019254.html#msg1019254
Zener diodes & lights/resistors

Or both as they seem to do different things (rms vs peak)

Seems to me (via reading, not experience) the typical failure model of compression drivers is peaks.

My calculations are such:

B&C DE25-16
10 ohms minimum impedance (measured)
28v - 80w peak
20v - 40w cont      (2hr pink noise 6dB crest factor)
10v - 10w thermal (based upon 6dB crest factor?) [not sure if this is correct as I am integrating knowledge gleaned from Ivan/others on limiting]

28v zener diode 50w
With 10ohm 50w resistor in series (could I double the resistance and drop to 25w to save money?)
Placed across (parallel with) the DE25

This seems to do the trick, 3% as a bonus to the normal 5% :) kinda expensive for 4x though...

In re-reading this:,138477.msg1289047.html#msg1289047
I might have flubbed the math for peak vs rms...

RXEF110 1.10A (10ohms gives me about a 12w continuous holding & 50w trip)
10ohm 25w resistor will drop me to 16v
Polyfuse & resistor are in parallel.
Series with xover/driver.

Placed after or before the xover?

Okay, I think I did all my math and calculations right...


6) Any thoughts on where to find this magical TD-'2' xover?
Seems Tom and Drew fussed around with the TD1 after SPL went outta business, I'd love to see/hear what they came up with...,109187.msg1019990.html#msg1019990

 on: Today at 05:06:34 pm 
Started by Dave Garoutte - Last post by Luis_Marquez
I did a quick video review of the Angler just for fun.
Great video! Corey. I am interested in a pair for this winter.

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