Members aortizjr Posted March 20, 2017 Members Share Posted March 20, 2017 I rent out rehearsal space and one of my customers had a mishap blowing the cab (Carvin BRX 10.4) and the amp (Carvin R1000) let out its magic smoke. Not sure what happened exactly, but I need stuff that can take a beating. Getting replacements from Carvin are $100 each, might as well see if I can find a used cab. I love the cab construction itself and I hate to be wasteful. Eminence Delta 10B's (16-Ohm, but can wire to 4 Ohm) are $69 and seem to be of similar specs (same size magnet at least). Also was thinking Eminence BP102's 4-ohm which are my go-to replacement speakers that are also $69. But I like the Delta 10's higher wattage. Cabinet dimensions are: 24.5" wide x 18" deep x 27.75" high Any suggestions? Link to comment Share on other sites More sharing options...
Members DeepEnd Posted March 20, 2017 Members Share Posted March 20, 2017 Can't say for sure but Carvin speakers used to be made by Eminence so they'd probably work. All else being equal I'd want the highest power handling I could get. The question is whether the speakers are a good match for the cab. Find a Thiele Small calculator and see if the Eminence you're considering are a good match. I usually use this one: http://www.micka.de/en/. For that matter, there's an SWR Goliath cab near you for $300 OBO: https://santafe.craigslist.org/msg/6048459512.html. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted March 21, 2017 Members Share Posted March 21, 2017 If the head blew it likely went DC and pumped 110V AC through the speakers. This is a common issue with solid state heads with certain designs. They call it going DC within tech circles but the term is kind of a misnomer. Normally, the power transistors are biased with DC and produce ac sine waves to generate music. When the transistors short out the DC bias shorts out. and the AC wall voltage bridges the power transistors and pumps the full 120VAC from the wall outlet straight through the speakers. I had this happen with a Blackface Peavey head about 10 years ago and it took out my prized Altec speakers. I heard the loud AC hum but was unable to shut the amp down in time. It fried the voice coils. If a band is playing loud the player might not notice it happening until its too late. You will want to check each speaker to see if they were all taken out. Sometimes it only takes out one or two depending on how the amp was wires. If the speakers were wired in series or a series parallel configuration typical with multi speaker cabs, the weakest speaker in series will blow first. The second speaker may still be good but you have to check both continuity and do a rub test pushing the cone in and out by hand to see if the voice coil got hot enough to warp it. If you notice a rubbing noise the paper and glue got hot and bulged the tight space in the magnet gap. The coil may still be good but because its physically warped it will produce fuzz tones with its rubbing and will need replacement. As far as getting replacements, I'd check and see what's in there now. If they are Carvin speakers I'd go to the Carvin site and look up they're specs including the wattage, Frequency response, SPL and resonant frequency. Its important you use those specs when choosing new speakers because the cab was Designed/Tuned to the response of those speakers. If you buy speakers with specs that are not right for the cab you can wind up with oddball bass responses. Some notes may boom out louder then normal and others my produce dead notes. It will seem like its a problem with the instrument having dead notes or the head failing to have the right EQ settings but its actually the amount of air in the cab not matching the drivers. This is not a big an issue with higher frequencies like guitars and guitar speakers. With Bass and PA gear its essential the speakers resonant frequency is a match for the cab. There are online calculators which allow you to build cabs based on the speaker specs. There are also methods of tuning cabinet ports using a milti meter so the speakers resonance produces maximum volume throughout its frequency range. If a speaker is close to having similar specs to the original and the port is tunable, you could tune the cab to match the replacement speakers. You can also do a certain amount of tuning by adding or removing cab insulation as well. Learning how to do it properly is the tough part. I learned to do it when I was getting my degree in electronics. I also worked for a company that installed sound systems in night clubs theatres and churches so I learned allot of it from guys who had been doing it for a living for a long time. If the port is an adjustable tube its real easy to do. Its like the slider on a trombone. As the pipe is lengthened the pitch of the note goes down, shorten the pipe the pitch goes up. When you have a meter connected to the speaker terminal, and have a sine wave pumping through the cab, then you adjust the port length, the meter will peak when the cab is in tune with the speaker resonance. The speaker will be moving at its maximum excursion producing the loudest note at that point. When the speaker is fighting the cabinets air because the resonance if off, the coil inductance produces back EMF and it causes a dip in the signal feeding the cab. The trick is to find the peak when adjusting the cabs port size. This can be a problem with factory made bass cabs. The port may simply be an opening and its size would need to be changes, it may be a bass reflex which would require cutting or adding to its length, or it may be a sealed cab where the air volume inside the cab would need to be increased or decreased. Luckily Bass frequencies are long and cabs may be designed for a low Q tolerance curve so even if the speakers are off a bit the cab may sound find. That combined with the heads EQ ranges you may be fine simply tweaking things in. I definitely compare the specs however. This may save you from some major hardship is the cab is way off for the speakers. I'd find speakers with the same Frequency response or greater, and as close to having the same resonant frequency as possible. The other specs like SPL will affect the loudness of the speakers, more then tone. New speakers are usually more efficient and have higher SPL levels so going to a higher dB can usually be a benefit, at least up to a point. Higher SPL usually means less cone weight and they can sometimes make a cone weaker and susceptible to distortion from low frequencies. As far as options go, they make these new Neo speaker now which make cabs allot lighter. It may be worth looking at reducing weight since you're needing new cones anyway. Cost wise you usually get what you pay for. Carvin makes some decent speakers. I have a set I put in my Yamaha PA cabs and they have sounded great for nearly 20 years now. I also have many Eminence, Celestin, JBL's and others. Its obvious the Carvin is a superior build to the Eminence, you can see it in the paper, the design and hear that quality in the speakers tone. If you're hard up for money you do what you got to do, but a step up from the stock speakers is going to cost you more then the stock speakers. Link to comment Share on other sites More sharing options...
Members aortizjr Posted March 21, 2017 Author Members Share Posted March 21, 2017 Thank you so much for the long response. I learned a lot from your post and I think others will as well. Good point on the amp going DC; with the age of this amp I am not surprised. I do repair a lot of amps and I have also seen similar things where there will be a blown speaker and a fried amp. However in some of the others it will blow a fuse, often a fuse that is encased in a chip and not obviously a fuse. In those cases I assumed that the speaker went first, shorting the voice coil then causing the transistor to draw too much power and is saved by the fuse. Would I be correct in that assumption? And by repair, I mean I can follow a schematic, order parts, have some basic theory and knowledge, but it is amazing how far you can get with a signal generator, a nail hooked up to a speaker, a multi-meter and a soldering iron. Back to the speaker I have been searching around for online calculators that a lot of sites and people refer to, but no links. All I can seem to find are speaker designer software that you have to pay for. I am fine paying for it, but then I have to learn how to use it. Can you provide links? Carvin unfortunately doesn't gives specs for their speakers and I E-mailed them last week with no response thus far. I also contacted Eminence with the dimensions to get their recommendation. They recommended the Delta 10B to maintain the 4 Ohm impedance. But I did pull and test each speaker individually as I have seen the first speaker blow as the weakest link in many other blown cabs. In this one 3 were completely shorted, and one has severe voice coil rub. So the hit was pretty hard. I am thinking with the R1000 now, it may be a better call to replace all the output transistors rather than the couple that are fried. I guess mainly to prevent this from happening in the future as the amp continues to age. Link to comment Share on other sites More sharing options...
Moderators isaac42 Posted March 21, 2017 Moderators Share Posted March 21, 2017 For online speaker calculators, a lot of people use WinISD. I use it myself, and like it a lot. http://www.linearteam.dk/?pageid=winisd Actually, I should correct myself. WinISD isn't an online speaker calculator, but rather downloadable. You download it and install it on your computer, and use it there. Link to comment Share on other sites More sharing options...
Members DeepEnd Posted March 22, 2017 Members Share Posted March 22, 2017 . . . If a speaker is close to having similar specs to the original and the port is tunable' date=' you could tune the cab to match the replacement speakers. . . .[/quote'] Unfortunately, the OP doesn't have that option. Here's a pic of a cab like his: [ATTACH=CONFIG]n31944759[/ATTACH] . . . Back to the speaker I have been searching around for online calculators that a lot of sites and people refer to' date=' but no links. All I can seem to find are speaker designer software that you have to pay for. I am fine paying for it, but then I have to learn how to use it. Can you provide links? . . .[/quote'] I already provided a link. Here it is again: http://www.micka.de/en/. It's designed for round ports so you'll have to measure the area of your rectangular ports and convert that to a circle but you should be able to get a rough idea how a given speaker will behave. Link to comment Share on other sites More sharing options...
Members aortizjr Posted March 22, 2017 Author Members Share Posted March 22, 2017 Yeah I saw the link upon review. Missed that somehow. Thanks for the help! Link to comment Share on other sites More sharing options...
Members DeepEnd Posted March 23, 2017 Members Share Posted March 23, 2017 Hey, that's what we're here for. Keep us posted. Link to comment Share on other sites More sharing options...
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