agedhorse

Adjustable input sensitivity isn't going to matter with the Avalon, it's MOL is +30dBu which will drive every power amp I have ever seen with loads of headroom to spare.

For that console, mic level will probably be more appropriate.

Do you have the TS parameters for the drivers used in the cabinet, or did you assume that they were stock drivers (which they likely are not, even if they look like it)

First, I am assuming that you man ShuttleMax 9.2 since there was not a 6.2 model in the Shuttlemax series. If it's a Shuttle 6.2, let me know and I will get you a copy of the correct manual. It depends on what you are trying to do. Line level is fine IF the console that you will be feeding is capable of handling line level (most pro consoles will have no problem), but if not you can switch to mic level (which is about 20dB lower) The controls only affect the DI when switched to post-eq mode. I have attached a copy of the owner's manual, there is all the info you need about how the DI section works. ShuttleMax 9.2 Owners manual.pdf

That's a pretty early build, before they started using ICEpower modules. You are probably going to have to find somebody qualified to reverse-engineer the power supply to determine what's really needed to be reliable. So far, you have succeeded in discovering a couple of ways it doesn't work... Does anybody know how many of these amps might have been built? This may explain why there are no spare parts available.

I have designed all kinds of products over my career, mostly pro audio and bass products, but some acoustic and electric guitar products too. This includes both high end touring electronics/speakers as well as lower end electronics/speakers (including for some popular brands/models). I first look at the requirements, both performance and cost, and then look to see what components are already on the market that I might be able to use or easily adapt into the enclosure that the product will need. I will also look at my historical designs to see if I have already designed a driver that might be suitable. I really don't like reinventing the wheel, especially at the higher end where the transducer engineers have spent a fair amount of time and money on. That said, I probably put more energy into the lesser models because I NEED to squeeze out the most performance possible for the least cost. This is true in all product lines actually. I find it more challenging to get the maximum performance out of the minimum cost, that's what separates the experienced engineers from the onanists. In the middle, giving up a dB or two of performance may not matter as much but at the low end every dB counts, and may be the difference in a viable product and one that's not. At the very high end, there's a LOT more effort placed on pattern control, the evenness of the response at the edge of the pattern, distortion, power compression (thermal and electromagnetic), and also structural since the cabinets may end up over your heads.

Yup, insignificant heating issues.

Yes, the air gap will reduce the enclosure heating effects somewhat which is why I keep mentioning worst case.

My calculations show that with 25 degrees C ambient, a 31cm x 31cm x 31cm wood box with nominal 12mm thickness, the final temperature after "forever" (called the asymptotic limit) will be 33 degrees C with an 8 degrees C total temperature rise. This is about what I would expect worst case, pretty much trivial. Here's one handy enclosure calculator, there are several. These sorts of formulas are also used in the heating and air conditioning industry too, the walls will have a thermal resistance, and if playing in the sun there will also be heat gain due to radiation. https://www.powerstream.com/temperature-rise-in-an-electronics-enclosure.htm

There's not much heat involved, the average dissipation is less than 50 watts worst case. Not going to be a problem at <50 watts of dissipation, it would take DAYS to raise the temperature 10 degrees C above ambient.

The amount of heat in the speaker being discussed is insignificant in the big picture

I only have a couple of saddle mounting systems left for those amps. Yes, be VERY careful when "home brewing" any hardware for an amp, I have seen too long screws ruin an amp beyond economical repair (aside from being dangerous).

Yes, it makes perfect sense IMO.

My experience and testing suggests that it's very dependent on the preamp and preamp pedal. There are a good number of pedals that have no issues driving power amps to rated output, the real issue is a shortage of specifications that provide the definitive answer. For example the TwoNotes revolt preamp's MOL is +11dBu (from their specs) and it operates from a standard 12V DC power supply.

Designers certainly sit down with these graphs when developing amps and speakers. They really aren’t intended for end users, especially because of the misunderstanding of the correlation between the graphs and how this translates to end results.

If you can’t understand the specs, than you either need to have somebody help you, by lucky or buy products designed to work together. It’s no different than taking gigs where you need to sight read, if you can’t do it, don’t take the gig and don’t criticize those who do.

Since I spent much of my career in the pro audio industry, there are a lot of misconceptions going around. First, it’s acceptable to power an amp at 2x the RMS rating of a speaker provided there’s is minimal clipping or OD/distortion components in the signal. As soon as distortion is added, no matter where in the signal path, this recommendation changes and the power handling of the speaker and amp (in RMS metrics) should be pretty similar, and for heavier distortion, and heavy compression, the speakers should be capable of greater power handling than the amp provides (by ~50% if you follow the guidelines of some driver manufacturers including JBL). This also assumes that a proper HPF is also used. Crown’s recommendation is being taken out of context when quoted for bass guitar amplification.

Nominal output level doesn't tell you all that much, what's more important is the maximum rated output level of the preamp. Generally, it needs to be about 6dB greater than the rated sensitivity of the amp to be sure you have sufficient drive capability to drive the amp into limiting (most pro audio power amps have internal limiting, and you want to be sure you can drive into this rather than clip the output of the preamp). Also, all numbers need to be expressed as volts rms.

Maybe, but this is the reason for published specs... to be able to answer these kinds of questions without guessing.

Since the Carbines are fan cooled, the orientation is not important PROVIDED the vents are not blocked.

Maybe, but there's no input sensitivity spec anywhere in their documentation so there's no concrete way to know for sure without trying it (or asking the manufacturer what the input sensitivity is for rated output).

In general, pro audio power amps are +4 to +8dBu rated sensitivity with the level controls fully up. Generally you will want 6dB of drive headroom to avoid overdriving the preamp while approaching the clip or limit point of the power amp. Some power amps also have exhibit lower sensitivity when driving unbalanced inputs, and many preamps have 6dB lower maximum output level when driving from unbalanced (or unbalancing via adapters) outputs. These are all things that need to be tested/verified to determine compatibility. It’s not always easy with the limited specs that are often provided.

Read the answers you got from me (and others) on talkbass where you posted the same question.

I would suggest that in general, testing at the preamp out is much safer, and likely to get results that are plenty close enough.

Duplicate post