So would that make this an 800 watt 8ohm cabinet? And if that's the case when pairing an amp with it what wattage should I go for?
Enjoy the benefits of a premium membership!
Upgrade Account
-
Welcome to TalkBass! Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Marshall JCM800 series... HELP!!
- Thread starter Barefoot greg
- Start date
Okay my wiring looks just like this one in the diagram
That's what I see as well.
Maybe someone will pop buy who can model the cabinet with the Carvin PS10s. Thiele Small parameters are available here Carvin's Thiele/Small Parameters, Speaker Specs, and Crossover Info
Other than that you will need measure the inside dimensions of the cabinet, as well as the port diameter and length.
With the right software, this information can be used to determine the system's low frequency response and how much power it can safely take.
Have fun.
Yep... an 800 watt 8 ohm cabinet..
Get a nice grunty amp and enjoy !!
Might be a bit of a stretch to find something 800w x 8ohm, you won't need a full 800 watts,
but if it can do 4 ohm, you might want to buy/build a second identical cabinet, then it would be real killer!!
Get a nice grunty amp and enjoy !!
Might be a bit of a stretch to find something 800w x 8ohm, you won't need a full 800 watts,
but if it can do 4 ohm, you might want to buy/build a second identical cabinet, then it would be real killer!!
This may not be a lot of help to you, but here it is anyway. I used to have the single 1 x 15 version and ran it with a Hartke HA2500. It sounded great, and was loud enough for me most of the time. I would still have it, but I decided to go with a pedal board with amp simulator as my tone....most of what I do nowadays is very low volume music, so I don't even need an amp, just go direct. When I bought the cab used at GC, I tried it with several different amp heads. It sounded good with all of them, but sounded great with the Hartke so that's what I went with.
The way that is wired has two pairs of speakers where each speaker of a pair is hooked up in series (8 ohm + 8 ohm in series = 16 ohms for the pair) and then the two 16 ohm pairs are hooked up in parallel which drops the ohms back to 8 ohms (16 ohms + 16 ohm in parallel = 8 ohms total load). That's actually a pretty common scheme to make an 8 ohm cab using four 8 ohm speakers.
I hope that makes sense. Basically you're turning 2 speakers into a 16 ohm total load pair by serially connecting those two speakers and another two speakers into another 16 ohm total load pair. Then you are using a parallel connection to hook the two pair up together. Parallel connections reduce the ohms load, so two 16 ohm pairs wired in parallel equals an 8 ohm load for the cabinet.
I hope that makes sense. Basically you're turning 2 speakers into a 16 ohm total load pair by serially connecting those two speakers and another two speakers into another 16 ohm total load pair. Then you are using a parallel connection to hook the two pair up together. Parallel connections reduce the ohms load, so two 16 ohm pairs wired in parallel equals an 8 ohm load for the cabinet.
That does help me, gives me an idea of what to try.
I found the Ampeg SVT 7 lastnight. It's a tube head that is capable of switching between 1000 watts @ 4 ohm and 600watts @ 8 ohm output.
If I understand this rightI could run that on the 8 ohm setting,(600watts) for my 4x10 and it should have plenty of power at that point but also leave me a little head room so I can get higher volumes out of the amp with out the signat getting distorted, correct?
And if say in the future I wound up with another cab or making a full stack I can always switch the Ampeg over to 1000 watts @ 4 ohm and be able to power something else if I ever needed to.
Seems practical to buy one amp that will not only do what I need it to now but leave room for growth.
I found the Ampeg SVT 7 lastnight. It's a tube head that is capable of switching between 1000 watts @ 4 ohm and 600watts @ 8 ohm output.
If I understand this rightI could run that on the 8 ohm setting,(600watts) for my 4x10 and it should have plenty of power at that point but also leave me a little head room so I can get higher volumes out of the amp with out the signat getting distorted, correct?
And if say in the future I wound up with another cab or making a full stack I can always switch the Ampeg over to 1000 watts @ 4 ohm and be able to power something else if I ever needed to.
Seems practical to buy one amp that will not only do what I need it to now but leave room for growth.
You could get the specs and do the math, but it might be worth contacting Carvin to inquire about those speakers in that cab.
The SVT 7 Pro is a hybrid head with a tube preamp and solid state class-D power section. The use of class-D is why it weighs in under 16 lbs. The 7 Pro is a respected and well reviewed head that is worthy of a professional musician.
It's always a good idea to try before you buy. Like most amps, the 7 Pro has it owns unique voice that you may love or hate. If possible try the 7 Pro with your Marshall and also with other speakers.
The efficiency spec for the Carvin PS10 is 94.7 db for 1 watt/1 meter. I believe this is a bit on the low side. If you play with a loud band, you may find that the 7 Pro has enough power to damage the speakers and you are still not loud enough.
Personally, I would try to determine if the Marshall is properly tuned before I cranked it. You might have to start a new thread to catch the interest of someone who has the experience and software. If the volume of the cabinet is compatible with the speakers, tuning can be optimized by varying the length of the ports. I would also try installing some speaker batting and possibly some additional bracing...top to bottom and side to side.
Fs of 57 Qts 0.5 xmax 4.0 voice coil 2" looks like 200 watts is peak also....... it might actually be safer to assume 400 watt cab....
Probably (depending on box dims and tuning) isn't going to go super low. Also has quite a bit of port area happening, so, yeah, it might be a good idea to run it through some software before assuming whoever got in there did it right. It does appear to be good work, aside from maybe needing a bit more bracing. Am I seeing it wrong, or is there some kind of dampening on the back panel and possibly sides? If not, yeah add a bit.
@barefoot have you gotten as far during your research to discover the box/speaker relationship that is so important to bass cab design? Just putting new speakers in there isn't a great way to do it. Hopefully whoever changed the drivers and added ports did the math first; or you may have simply picked up someone else's problem fartbox.
When you do get a ballsier amp hooked up to it, start out slow and low with the volume and take it up incrementally. Leave your tone-shaping knobs/switches/EQ flat or off/cut, too. Add little boosts at a time with these too. Any indication of fartout is OVER the cab's capability. Like Wasnex said, you just might find that it just won't get as lout as you hope with the tones you're after. Watts really don't mean all that much when it comes to a bass cabs real-world power handling.
Probably (depending on box dims and tuning) isn't going to go super low. Also has quite a bit of port area happening, so, yeah, it might be a good idea to run it through some software before assuming whoever got in there did it right. It does appear to be good work, aside from maybe needing a bit more bracing. Am I seeing it wrong, or is there some kind of dampening on the back panel and possibly sides? If not, yeah add a bit.
@barefoot have you gotten as far during your research to discover the box/speaker relationship that is so important to bass cab design? Just putting new speakers in there isn't a great way to do it. Hopefully whoever changed the drivers and added ports did the math first; or you may have simply picked up someone else's problem fartbox.
When you do get a ballsier amp hooked up to it, start out slow and low with the volume and take it up incrementally. Leave your tone-shaping knobs/switches/EQ flat or off/cut, too. Add little boosts at a time with these too. Any indication of fartout is OVER the cab's capability. Like Wasnex said, you just might find that it just won't get as lout as you hope with the tones you're after. Watts really don't mean all that much when it comes to a bass cabs real-world power handling.
I hadn't gotten to the cab/driver relationship point yet so this is good for me too learn it on I guess 
I'll take exact measurements of the internal cab dimensions, aswell as measurements of the length on all of the ports when I get home tonight.
Is there a certain wood I should use when bracing the inside of the cab? The original box is a multiple ply wood construction. It's quality sheeting aswell, almost clear( aka no knots) the center post that braces the back of the cab is either southern yellow pine(not likely being that marshals are from England) or more likely hardwood by looking at the end grain. Should I try and use the same type of wood for the bracing or would say pine from the local hardware store be fine?
And when I brace it will using the center cross brace as a central starting point and going up down left and right from there be correct? The extra bracing is to prevent warping in and out while the speakers are operating if I understand it right
Sorry for the long book I just wrote, bear with me folks haha but thanks again everybody
I'll take exact measurements of the internal cab dimensions, aswell as measurements of the length on all of the ports when I get home tonight.
Is there a certain wood I should use when bracing the inside of the cab? The original box is a multiple ply wood construction. It's quality sheeting aswell, almost clear( aka no knots) the center post that braces the back of the cab is either southern yellow pine(not likely being that marshals are from England) or more likely hardwood by looking at the end grain. Should I try and use the same type of wood for the bracing or would say pine from the local hardware store be fine?
And when I brace it will using the center cross brace as a central starting point and going up down left and right from there be correct? The extra bracing is to prevent warping in and out while the speakers are operating if I understand it right
Sorry for the long book I just wrote, bear with me folks haha but thanks again everybody
In a nutshell, the box should be built based on the specific performance and mechanical specifications of the driver or drivers going into it. These are the Thiele Small parameters (T/S). Just tossing whatever drivers into whatever box will very likely result in any one or more of the following: bad speaker performance, low power handling, damage to the speaker, death of a unicorn, angel tears, I-told-you-so's, or rips in the space-time continuum.
There are software programs for this, WinISD is free, and does a decent job telling you how a given speaker should perform in a box of a certain volume, sealed or ported.
My concern from your initial post was that the cab was sealed and just randomly swapped out to the Carvins with no forethought or research, then wired to 32 ohms. Since the wiring was done correctly, and the ports added (which do seem to be at least the same length) I think you may find the work and research was done; at least I'm hoping for you.
The bracing can be hardwood or ply. It's purpose is to keep the cabinet rigid so there is no energy lost shaking it... any energy you send to the cab should be coming out of the speakers, not making your box a giant vibrator.
There are software programs for this, WinISD is free, and does a decent job telling you how a given speaker should perform in a box of a certain volume, sealed or ported.
My concern from your initial post was that the cab was sealed and just randomly swapped out to the Carvins with no forethought or research, then wired to 32 ohms. Since the wiring was done correctly, and the ports added (which do seem to be at least the same length) I think you may find the work and research was done; at least I'm hoping for you.
The bracing can be hardwood or ply. It's purpose is to keep the cabinet rigid so there is no energy lost shaking it... any energy you send to the cab should be coming out of the speakers, not making your box a giant vibrator.
You might secure the center post and try it before going to the trouble of adding additional bracing. If you decide you want to add some bracing it should not be necessary to use such a big piece of wood as the center piece as that will add unnecessary weight. I would run one brace from side to side and one brace from top to bottom, tacking each to the center pole. IMHO the braces will be more effective if you can put a little pressure or tension on them. The goal is to stress the panels in order to make them more rigid and increase their resonant frequency.
Well that escalated quickly! Haha good to know, after all unicorns have been on the endangered species list since Noah forgot to load them on the boat I certainly wouldn't want the sound of me playing my bass to be the reason why another one ***** the bed.
thieves and small were the two guys from Australia back in the day who did all the research on this stuff right?
Ohh so that's what y'all meant when ya asked about the t/s info! Gotcha
Ohh so that's what y'all meant when ya asked about the t/s info! Gotcha
When I measure the ports do I measure from interior face of the cab to the tip of the port sleeve or inside the sleeve from one end of the pipe to the other?