8" MTM questions...

[emilime75]

I did a search and I know someone asked some similar questions already, but I have a somewhat different plan/goal in mind. I need a pair of compact PA speakers for a small practice space and for use in small clubs/venues but with good sound quality and decent output. What I have in mind is the following, each cabinet would consist of...

2 Eminence Alpha 8A's
1 JBL 2425H
1 Dayton 8" Waveguide(for the 2425H)

I was thinking the 2 Eminence 8's would be able to keep up with 1 JBL + Waveguide. The cabs(JBL Cabaret 4691B) that are donating the 2425's are originally crossed over at 1.5k. I can copy the original JBL highpass section for the tweeter(maybe) and build my own low pass for the Eminence 8's. I want to keep the baffle as narrow as the drivers/waveguide will allow for asthetic reasons, so copying the original crossovers for the tweeter may not be an option if any BSC was incorporated in the original design. However, the original design also has an adjustable "L-Pad" knob so that just may work fine. These will also be used with subwoofers, so low bass is not expected or needed from them. My basic questions about this idea really are these...

1. What are the pros/cons of an MTM or TMM for a speaker like this? I thought an MTM with 8" woofers and an 8" waveguide would look nice. But if a TMM design would be better, than I'd go with that. I do understand the fact that the tweeter should be placed high for PA pirposes so that it travels and does not get blocked/absorbed by the first few rows of people.

2. Does anyone have any crossover designs for the Alpha 8A? I will be using 2 in each cab wired parallel.

I am also trying to do this on a small budget and I already own 4 Alpha8A's and the JBL 2425H's. The only things I would need to buy are the waveguides and the appropriate adapters to mount the drivers to the waveguides and then of course the crossover components. I probably have enough plywood in my shop to build them. Any other thoughts/suggestions would be greatly appreciated.

[Paul O]

I like the design personally, if these are to be used occasionally as monitors then the MTM layout makes more sense and they'll still be small enough to get the horn up above the crowd for FOH duty. I don't think you'll find any BSC in a pro audio crossover, maximum sensitivity is more important so simply target the best acoustic crossover response possible and EQ to taste.

[billfitzmaurice]

It's just fine if you never intend to expand the system and the capability of the Alpha 8s is sufficient. In a 2 cu ft box tuned to 60 Hz they'll work fairly well, with a maximum output of 114dB, which is OK for smaller gigs, house partys, etc. Of course you'll need a sub for substantial output below 80 Hz.

[emilime75]

It's just fine if you never intend to expand the system and the capability of the Alpha 8s is sufficient. In a 2 cu ft box tuned to 60 Hz they'll work fairly well, with a maximum output of 114dB, which is OK for smaller gigs, house partys, etc. Of course you'll need a sub for substantial output below 80 Hz.


I do definetly plan on using a sub. I have a Rane AC22 that will be used to cross these over to the subs somewhere between 80-120 Hz, I planned on playing with that once they're built. I am also considering a 3 way electronic crossover and biamping the mid-hi boxes. I don't plan on expanding the system, if I ever find a need for more output I will build/buy different speakers, but these will be primarily used as stated in original post.

I think I will stick to the MTM design, are there any pros/cons to using waveguides in narrow baffled speakers. I would like to make them as narrow as possible, so probably only about 9-10 inches max.

[billfitzmaurice]

are there any pros/cons to using waveguides in narrow baffled speakers. .No pros, con is poor sensitivity. Use a proper horn.

[emilime75]

Would you mind elaborating a bit on what exactly you mean by "use a proper horn"? I know you have a lot of knowledge and experience with PA and audio in general, I'd like to hear your thoughts.

[billfitzmaurice]

Would you mind elaborating a bit on what exactly you mean by "use a proper horn"? I know you have a lot of knowledge and experience with PA and audio in general, I'd like to hear your thoughts.
Waveguides don't load HF drivers to the extent horns do, so sensitivity is considerably lessened. They also don't have the vertical pattern control of horns. That's not a concern with consumer speakers, where more often than not a compression HF driver has far more sensitivity than the woofers and pattern control isn't an issue. But in pro-sound sensitivity and pattern control are major issues. It's why pro-sound uses HF compression drivers, as opposed to dome tweeters etc.