stevie

[quote name='obbm' timestamp='1474634081' post='3139448'] In addition they are response for post-sales warranty so if your Prodigy dies it will have to back to them for it to be fixed at their cost, assuming that it is still within the warranty period. All of this is paid for from the mark-up on the products they are selling.... [/quote] Sorry to nitpick, because I agree with everything else you have said, but the manufacturer normally refunds the distributor for repairs they have to carry our under warrranty. So that's not one of their costs.

Yes, kerbs and stairs are probably the big problem for dolly boards, although I've never used one myself. My trolley is a sack barrow type. I want to avoid cutting holes in my cab for rear castors, or spending money on a dolly board for that matter, when a separate trolley (which I already own) is the best solution anyway. I think I'll give the trolley a go first. Unless someone has a convincing argument in favour of another solution. Thanks for the input!

That's a step too far in the woodworking department for me, Mark. So the Barefaced uses 3-inch castors and large rubber feet at the front to make the cab level. OK. This is a lot more complicated than I expected.....

[quote name='bertbass' timestamp='1476291212' post='3153120'] 3 inch might be better as cracks in pavements etc, won't be noticed as much but you might have to raise the front of the cab a bit so that it's level. Another option is 4 wheels on the bottom of the cab and turn it on its side when in use it then becomes a high dolly and you can wheel loads of gear in at once. [/quote] OK. I think I get that. So with 3-inch inset wheels on the back, the cab would not be level. Would larger rubber feet on the front fix that, or not? The cab design is vertical and won't work properly on it's side. 4 wheels on the bottom should be OK in my limited experience, but it might be a bit top-heavy when moving it.

I'm now more confused than when I asked the question. So is a dolly board a better solution than a trolley or permanently attached castors?

[quote name='deksawyer' timestamp='1476275699' post='3152896'] What's your opinion on active versus powered? [/quote] If you already have a power amp in-cab, you are throwing away a lot of the benefits of digital technology and DSP by not using an internal active crossover. The HF power amp section doesn't have to be as powerful as the main one - so the weight penalty isn't huge. An electronic crossover allows you to time-align the drivers accurately and use steeper slopes than you would otherwise use. Plus, you can then tailor your limiting so that it acts independently on each individual driver, which helps with reliability. The downside is that there is an extra cost involved. Technically, it is a superior solution, which is why all the top-end active cabs use this approach - and even some cheapo ones like the Alto TX12, which cost about £150 each. I'm a great fan of passive speakers personally. But that's a different kettle of fish and they do have to be done properly.

[quote name='stingrayPete1977' timestamp='1476268422' post='3152808'] I didn't know they were active! [/quote] It doesn't look like they are active. They are powered. I think most people would expect an active system (two power amps and an electronic crossover) for that money.

I was wondering about what size to use. Wouldn't 3-inch be better?

I'm in the middle of building a 15" cabinet about the size of the Ashdown ABM or Trace 1153 and am looking for some pointers on wheels. I have a set of 3" rubber wheels on my Ashdown Mini 15 and they work quite well, but I'm unsure of whether they will be right for this larger cab. So I'm thinking either 4 x 4" castors (probably a bit big) or those recessed castors that fit into the bottom edge of the cab allowing you to tilt and roll. A top handle is in place that would allow for this. http://www.penn-elcom.com/default.asp?MC=01120801&LG=ENG&title=corner-castors What are your experience with those - positive or negative? Or would I be better off with my aluminium trolley?

I agree with the others. It's a choke. It's got to be from the tweeter circuit because if it was from the LF circuit you wouldn't have any sound from the main driver now. It sounds like it hasn't been fixed down very well and was held on mainly by two soldered wires, which have snapped off. You need to trace the wiring from the L-pad (the tweeter volume control) back towards the input. It should lead to the crossover. If there is enough wire sticking out of the choke, you might be able to repair it - otherwise you'll need a new choke. If this assumption is correct, you are now putting excessive power through the tweeter. So you really need to fix it, even though it might not sound any different.

Sounds like all root notes to me. One sustained note per bar, with an eighth note lead-in every once in a while at the end of the bar and an occasional octave. You put your finger on it yourself. It's country. Keep it dead simple.

I've re-checked one cabinet that I have here with a slot port, and my software is 100% accurate compared with the impedance measurement. I also recalculated the Cab Diary speaker and it's only 2Hz away from what we actually measured. Just for information, really, as what matters is the actual measurements on the cabinet.

Yes, I think you're right, Phil. See my comment in the Beyma thread that's currently running.

Looks OK. I get 89 litres tuned to 44Hz, although since my recent failures with my tuning software I'd take the latter figure with a grain of salt. The limiting factor is the size of the ports. Increasing them to 4" diameter (by 5" long, but perhaps someone would double-check) would help, if that's possible. The low end response is 15dB down at 40Hz. Excursion-limited power handling would be close to 500 watts, which is pretty good.

[quote name='Phil Starr' timestamp='1475523712' post='3146671'] I think he may be as old as we are Stevie [/quote] Sounds like it, Phil.

Inches? Really?

BoB said earlier that they have a "proper" crossover and not just a high pass filter. If it's a 2nd-order crossover designed for 4 ohms, connecting it to an 8-ohm load will cause a nasty peak in the midrange and pull the impedance down below nominal. If it's just a 1st-order (inductor only), it will lower the crossover frequency and depress the mids. Either way, not good.

Really appreciate this. Thank you.

Fascinating! John, I just re-entered the numbers in your last post into my software and get 57Hz for the slot port, which is still quite a bit off. My software is actually deducting volume for the port and the driver, which should make it more accurate, but there's obviously something wrong that I can't quite figure out yet. I did the same with cab no. 2 and get 55Hz compared with your measured 61Hz. That's also rather disappointing. Bassbox Pro is usually spot-on with round ports, as we found when we meaured Phil's prototypes. When I have a bit more time, I'll have a fiddle with WINisd, although I believe Phil uses WINisd and he got the same figures as I did in our earlier calculations. I really like your side-ported version, by the way, as it leaves space for an optional tweeter or midrange driver. Phil originally built a slot ported cab, but with the ports at the end of the box. We discarded that because of a nasty standing wave that was not present in the box with round ports. We assumed at the time that this was because the slot port had made the internal dimensions square . This thread would indeed make a useful addition to the Cab Diary. Maybe one of the mods could pick it up and stick it on the end. [Edit] I would just add that your measurements demolish my theory that cab mis-tuning was the cause of your damaged driver.

It seems to be a common problem with DJs. Otherwise, I agree: it's not as common as it used to be.

That's not correct, Bill. You're assuming that the driver is matched to the cabinet, which it isn't. A QB3 cabinet for a Beta 10 is nearly 100 litres. Even Eminence suggest using a 64-litre cabinet per driver, and it still peaks then. To try to prevent this from becoming really confusing, I've modelled the driver using 90 litres as the internal volume for the Peavey cab - that's probably not too far out. This is what the frequency response looks like: The yellow curve is the sealed box and the pink one is the vented one. Personally, I'd take the sealed curve anyday, but some people like the peaked response and that's their choice. I also modelled power handling. The sealed cabinet reaches the driver's 3mm xmax at 50 watts input, the vented cabinet at 75 watts. So the choice is between a 200-watt sealed box or a 300-watt vented box. Having said all that, Bigwan needs to take it one step at a time, and the first thing to do is to connect the drivers directly to the input, bypassing the crossover. That could be the real problem.

Very good point, BoB. I agree, there will definitely be some weirdness going on if it's a proper crossover (you don't come across those very often). Better to try it with the crossover bypassed first. To convert the crossover to 8 ohms, double the size of the inductor and half the size of the capacitor going to the LF drivers. In the unlikely event that there is a resistor in the LF circuit, you can probably leave it as it is.

That's how those drivers sound in that cab and there's probably very little you could do to the porting to change that. The Beta 10s are suitable for used in sealed cabs. How well they will work in the Peavey depends on its internal volume. Why not simply close up the port by stuffing some cloth inside, and have a listen? If it sounds promising, take it from there. Sealing the cab will reduce the amount of low bass. If the problem you are experiencing is excessive, boomy bass, sealing the cab could be a good solution.

I wouldn't rely on Xlim too much, Phil. There is a myth going around that Xlim is the maximum excursion a driver can take before it gets damaged, but that's plain wrong. Xlim is a short-term physical limit that relates more to the suspension, cone and coil former rather than to the voice coil. When you go past xmax, power compression starts to kick in with a vengeance and you put power into the coil that has nowhere to go. The magnetic gap provides an important path for cooling the voice coil. Push the coil too far out of the gap, and it doesn't get cooled properly. The voice coil can reach its thermal limit well before it reaches Xlim, as I'm sure many on this forum will testify. My guess is that this is what has happened here, but like anything else, it's impossible to be sure at a distance. If overheating is the cause, the voice coil will be discoloured. Here's a useful diagram showing xmax and xlim: [url="http://www.subwoofer-builder.com/xmax.htm"]http://www.subwoofer...er.com/xmax.htm[/url]