Bill Fitzmaurice

[quote name='Al Heeley' post='889401' date='Jul 8 2010, 07:01 AM']I asked in the Hartke subforum about how to rewire the 410 cab as a 4ohm to get the max push out of the amp and was told it could not be done.[/quote]Nor is it generally worthwhile anyway. Few cabs will take more than half their thermal power rating before exceeding excursion limits. Even were that not an issue you'd only get 2dB additional output from a 4 ohm versus 8 ohm cab. That's audible, but just.

[quote name='bigjohn' post='888848' date='Jul 7 2010, 02:36 PM']Indeed. If you we're going to run them parallel I'd have them rewired to give them greater impedance. You won't notice that you're not drawing "the full power" from the amp. Or have them rewired so you can run them in series.[/quote] The jacks on the back of the amp are parallel wired, as are the paired jacks on the cabs. It doesn't matter whether you use both jacks on the amp or run one cable to one cab and daisy chain the second cab from the first, it's still parallel wiring. You only get series wiring when you use a specially made series wiring harness.

[quote name='Al Heeley' post='888648' date='Jul 7 2010, 11:54 AM']Peavey Tour 450 head & 2 hartke cabs: Does it make any difference if I wire each cab from the two separate outputs on the amp, or daisy chain them from amp to cab1, then cab1 to cab 2? Is there a best method?[/quote]Electrically both methods are identical, a parallel load. The only potential advantage to running the cables each separately to the amp is then the current flow and cable resistance loss is divided between them. That's only an advantage if the cables are shy on current capability and have high DCR from being under gauged.

[quote name='thinman' post='878792' date='Jun 27 2010, 08:22 AM']I was worried about phantom power with my amp too. OBBM, who posts on here, suggested the following that works well and is about as cheap as you can get: On a XLR pins 2 and 3 are both at +48v, i.e. common, relative to pin 1 ground. If you simply disconnect pin 1 there's no circuit for the phantom voltage any more (and it also cures any earth loop issues). The signal out is carried by pins 2 and 3. I made a short tail lead with pin 1 disconnected and it does the trick nicely.[/quote] That might lead to grounding issues with some boards. The better option is to wire 1uF 50v tantalum capacitors in series with the pin 2&3 leads, and they're so small that they'll fit inside an XLR shell.

[quote name='fatback' post='873553' date='Jun 21 2010, 10:22 AM']Bumping in hope of an answer to this interesting one... [/quote] Get a couple of inch high rubber cabinet feet, screw them to the rear of the cab top to act as stops to keep the amp from sliding off.

[quote name='Bilbo' post='871148' date='Jun 18 2010, 04:29 PM']Most desks let you turn the phantom power off....... at least that's what I thought.[/quote] It's usually on or off globally for all channels, unless it's a high end desk. A transformer or capacitive coupled DI isn't bothered by phantom power, but some DIs inexplicably aren't one or the other, inexplicably as the cost of isolation caps is a few pence. Check with the amp manufacturer.

Tilt it back. Lifting it on a table creates a loss of boundary reinforcement in the midbass. In a boomy room you may find that beneficial, but otherwise tilting it back to put the driver centers aiming at your ears is better.

[quote name='Matty' post='866386' date='Jun 13 2010, 03:37 PM']I've always imagined them to sound tinny, perhaps swayed by the apearance?[/quote]Absolutely swayed by the appearance. The only instance where a metal cone will sound different than a paper cone is when you hit them with a stick. There's no particular advantage or disadvantage to aluminum cones except as marketing tools.

Add a four inch duct to the port.

[quote name='Phil Starr' post='857859' date='Jun 4 2010, 07:10 PM']There's a problem with most 4ohm drivers as well. they are usually made by just changing the voice coil for a shorter one which ...reduces excursion (Xmax)[/quote]Not if they do it the right way, by reducing the number of windings on the same former. But your point is valid, not every driver manufacturer does things the right way, and you must pay attention to all the driver specs, not just impedance.

[quote name='cameltoe' post='857651' date='Jun 4 2010, 03:29 PM']So with the RMS output almost doubled from going 8ohm to 4ohm, through a speaker that can handle the power, I'd really see no extra (real world) volume?[/quote]Not enough to make it a worthwhile venture. What would work if you must stay as small as possible is a high powered compact amp, at least 300 watts into 8 ohms, and a fifteen with high sensitivity and long excursion, such as an Eminence 3015. With a low powered amp the only way to get high output is with at least two drivers.

[quote name='cameltoe' post='857309' date='Jun 4 2010, 09:46 AM']However, knowing absolutely nothing about amps, I wondered if it was possible to get the full 150w from my Trace WITHOUT adding a cab? Could I, for instance, swap the 8 ohm driver for the appropriate 4 ohm driver to acheive max volume?[/quote] Full power is moot; the difference between what you might get with a 4 ohm driver versus 8 ohm is 2dB, and that's best case. Adding a second identical speaker gets you 6dB, which should do the trick.

[quote name='Randy_Marsh' post='849048' date='May 26 2010, 06:54 PM']I'm looking at a Hartke Cab for sale on here. It's rated 150watts RMS at 8ohms and i was wondering if i could increase the power and what it would involve, as i was hoping to get a cab with a bit more kick...[/quote] Only by replacing the drivers. Just buy a better cab.

They're parallel jacks, either can be used as input or output.

[quote name='Mr. Foxen' post='839089' date='May 16 2010, 01:37 PM']Is this mostly for when you are cramming loads of power into it? I have noticed old cabs have small ports, guessing its because the 2 15s are for sensitivity for lower powered valve amps, and just didn't take those sort of power levels.[/quote]If you go back 20 years or more when drivers with 2mm or less excursion limits were common, limiting them to 20 watts before going non-linear, then yes, you could get away with smaller ports. I wouldn't call 100 watts per driver loads of power, and most B-Ws will take that. If given that much the OP would get chuffing big time.

[quote name='umph' post='839036' date='May 16 2010, 12:33 PM']did you just stick a random port in or did you tune it properly to the drivers? Nice work by the way[/quote] +1. It may be OK tuning wise, but it's far too small and will chuff at high levels. Two ports with the proper duct length will work much better; minimum recommend diameter with fifteens is 6 inches [i]per driver[/i]. While at it, the cab could use panel to panel bracing fore to aft, side to side and top to bottom. Doing so with even single 1 inch wide braces will quadruple the panel stiffness.

[quote name='OldGit' post='836840' date='May 14 2010, 03:42 AM']Can anyone identify exactly which models they are? Head and Cab. It just says "Bassman Amp" on the head.[/quote] [url="http://www.ampwares.com/"]http://www.ampwares.com/[/url]

[quote name='Ancient Mariner' post='834199' date='May 11 2010, 08:32 AM']Resistance and impedance are not the same thing, and what you are measuring is resistance. Impedance varies according to, among other things, the frequency of the signal sent through the speaker.[/quote] +1. OP, read this: [url="http://wiki.basschat.co.uk/info:amps:impedance_and_wattage"]http://wiki.basschat.co.uk/info:amps:impedance_and_wattage[/url]

[quote name='Mr.T' post='828812' date='May 5 2010, 01:55 PM']Does that mean it's Ok for me to think that my new cabs sound good? [/quote] Some of the fave rigs of all time are Ampeg flip-tops, B12s, B15s, etc. They have one of the worst responses imaginable, with a huge midbass response hump and no real low end. That doesn't mean they don't subjectively sound good.

[quote name='Mr.T' post='828431' date='May 5 2010, 08:46 AM']Would 60 litres be classed as a 'small' cab for a 12" driver? They are a similar size to the Aggie 12's, and I don't hear too many people complaining about a lack of low-end from those. But hey.... Horses for courses![/quote]60l is adequate for twelves with Qts of .4 or less. As for the perception of low end response, the human ear is very inaccurate; most people are about an octave low in their estimates of the frequency they're hearing. Low 'B' players who swear they're knocking down walls with 32Hz output are actually hearing the 2nd harmonic at 64Hz. Good thing, as otherwise even a Fridge wouldn't be up to 5 stringer needs.

Eminence has been using Klippel Analysis to measure xmax on their drivers for about four years. It's defined as excursion at 10% THD. It's a far more valid method than coil depth/plate thickness methods, which are neither accurate nor consistent. For instance, in the case of under-hung coils that method gives an xmax of zero. Comparing the Klippel versus coil/plate figures on Eminence drivers the Klippel figure runs about 15% higher. Using that standard the BN10300S would come in around 2.5mm, and the NTR-10 2520D around 4.9mm. As to why Klippel is not universally employed it's simply a matter of the manufacturers not buying the gear.

[quote name='JTUK' post='825908' date='May 2 2010, 04:23 PM']Well, crap gear back then was crap gear..we all prorbaly had it at some time. Got to disagree with the stack influence factor though... Same rig, different room has had a massive effect on my sound from time to time. That is why I say it is a bigger influence.[/quote] Room modes are problematic for sure, but one way to minimize their effect is with vertically aligned drivers, which have far more uniformity from room to room, and basically just sound better no matter what room you use them in.

[quote name='JTUK' post='824144' date='Apr 30 2010, 10:25 AM']because most of us would run a mile from having to revert back to the old PA columns for bass. [/quote]In the late '60s I used a Kustom Tuck and Roll 4x12 PA column, it had as much output as a Fridge, with better tone to boot. [quote]It just looks total cack... and I'd be thinking the variable of the room has far more influence between sounds than how you stack them.[/quote]And that's why no one sells them. How you stack them has more influence over the sound than the room. Your not knowing that isn't the exception, it's the rule, unfortunately.

[quote name='Badass' post='822775' date='Apr 29 2010, 05:17 AM']Anyone else do it the way described by GK?[/quote] Not me. I set my gain for the desired level of grit, then I set the master for the desired level. It tends to be the other way around with a PA console, where you want it as clean as possible.

[quote name='chris_b' post='821170' date='Apr 27 2010, 04:02 PM']Isn't Bugera and Behringer part of the same company? Nuff said![/quote] Bugera is the silly quasi-Italian name that Behringer pulled out of thin air to stick on musical instrument amps, so that the ill-informed wouldn't realize it was Behringer until it was too late.