mike257 Posted May 25, 2011 Share Posted May 25, 2011 Alright guys, A band I've just started teching for are having some reliability issues with the bass rig. It's an SVT2-Pro and a 410HE. The valves have recently been changed by a previous tech, but looks like the bias hasn't been set properly. Had some problems with the amp intermittently cutting out. I've pointed out that they're running an 8ohm cab off a 2/4ohm valve head, which is going to cause some upset. What I was wondering is if anybody knows the impedance of the indivdual drivers in the SVT410HE as I haven't had the chance to get the back off yet. If they're 8 ohms I can rewire to 2 and match it properly to the amp - if they're 32 then it's off to the shops! If any of our wiser members want to chip in with suggestions, feel free! Cheers, Mike Quote Link to comment Share on other sites More sharing options...
Tinman Posted May 25, 2011 Share Posted May 25, 2011 I'd say that they're more likely to be 8 ohm wired in series/parallel. Quote Link to comment Share on other sites More sharing options...
Lozz196 Posted May 25, 2011 Share Posted May 25, 2011 I`m fairly sure that`s the case, as Lean Business sell a four-pack of 4 ohm Eminence BP102s, stating that these are an ideal replacement/upgrade for a 4 ohm Ampeg 4x10. Can`t think why they would wire up their 8 ohm cabs different to their 4 ohm ones, tho you never know............ Quote Link to comment Share on other sites More sharing options...
alexclaber Posted May 25, 2011 Share Posted May 25, 2011 I believe they're the same 32 ohm drivers used in the SVT810. You may struggle to find a 4 or 16 ohm 10" which suits a sealed cab. Look for high Qts. Quote Link to comment Share on other sites More sharing options...
mike257 Posted May 25, 2011 Author Share Posted May 25, 2011 [quote name='alexclaber' post='1244489' date='May 25 2011, 04:59 PM']I believe they're the same 32 ohm drivers used in the SVT810. You may struggle to find a 4 or 16 ohm 10" which suits a sealed cab. Look for high Qts.[/quote] Hi Alex, That's what I thought they might be, but was hoping I'd be wrong! Would the Eminence BP102 drivers that Lozz suggested be suitable, or am I better off suggesting he changes his cab setup? Am I overstating the damage the 8 ohm cab will do to the 4 ohm SVT2, or is it a likely contributor to his reliability issues? Cheers for your ace advice (as always!) Mike Quote Link to comment Share on other sites More sharing options...
longtimefred Posted May 26, 2011 Share Posted May 26, 2011 id say get rid of the cab and get a 4ohm equivilent. Running an 8ohm cab with a 4ohm valve head is bad bad bad bad bad. It can be bad news for your amp and an SVT2 aint cheap to replace. Always run valve heads using the correct impedance. Personally if you were going to change the cab, and wanted to keep to a 4x10, i would go for what i have which is the SVT410HLF as they are amazing for a 1 cab setup. totally recommend it. Quote Link to comment Share on other sites More sharing options...
mike257 Posted May 26, 2011 Author Share Posted May 26, 2011 (edited) It's not for me, it's a band I'm working for - if it was my dollar getting spent I'd buy an SVT610 - like I already have I'm going to look into replacing the speakers, as replacing the cab and it's flightcase is a big dollar purchase compared to the cost of new drivers. Any feedback on the suitability of the Eminence BP102-4 or alternatives would be more than welcome! EDIT: Alex/all you other experts - Eminence quote .38 Qt's, is that the right end of the spectrum for sealed cab use? Cheers, Mike Edited May 26, 2011 by mike257 Quote Link to comment Share on other sites More sharing options...
longtimefred Posted May 26, 2011 Share Posted May 26, 2011 lol yes after i posted i saw that you had the 610 and thought "doh! should have kept mouth shut, he already knows the HLF rocks!" Fair enough about replacing the speakers, just hope you find some that dont alter the sound of the cab too much. Good luck with your mission bud. Quote Link to comment Share on other sites More sharing options...
mike257 Posted June 3, 2011 Author Share Posted June 3, 2011 Had a brainwave whilst on the throne this morning (where all man's greatest achievements of thought are born) that may solve this problem, although I want to run it past you better minds first! If the amp is looking for a 4 ohm load, rather than hacking away at the cab, would chaining an 8 ohm dummy load off in place of a second cab satisfy it? That way, the bassist in question gets to keep his cab all original, amp sees a matched load - everybody wins! If there's a staggeringly obvious technical reason why this wouldn't work, please let me know Quote Link to comment Share on other sites More sharing options...
razze06 Posted June 3, 2011 Share Posted June 3, 2011 If you add another load (8 ohm dummt resistor in your case) in parallel, you'd be splitting the signal power in two, with the speakers getting one half, and the dummy load the other half. In other words, you [u]may [/u] be presenting the right impedance to the amp, but you'd be throwing half of that power away. Quote Link to comment Share on other sites More sharing options...
chris_b Posted June 3, 2011 Share Posted June 3, 2011 Get an 8 ohm 210 to sit on top of the 410. Cheaper, less hassle and more effective. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted June 3, 2011 Share Posted June 3, 2011 four 8ohm speakers will give you what you want, 2 ohms overall but I'd seriously consider the other options first. A dummy resistor will take half the power and will have to be a fairly impressive resistor to dissipate 150W, not a good option. A second cab will work and give you potentially a bit more sound but will change the tone. Changing the speakers will also change the tone and it won't be an ampeg any more. It might be better of course. Unless you have years of experience it won't be a predictable change of tone, there are so many variables. If you are going to spend £200 on speakers then what would you get for the cab second hand? Add the two together and that is what you could spend on a new cab which you could try before spending your money. Qts of 0.38 is perfect for a reflex (ported) cab but a bit low for a sealed cab, it might work but could well be a little overdamped. You'd want to model it with WinIsd or something similar as there are plenty of other things which would affect the outcome. If it was your cab then it would be up to you to take the risk of an unpredictable outcome but if it is for someone else I'd recommend they look at getting a more appropriate cab and selling this one to pay for it. Quote Link to comment Share on other sites More sharing options...
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