My starter rig - Mostly DIY.

[rumblinbass]

I'm not sure if this means much to this thread but I believe the Eminence Alpha 8MR is self contained - you don't need to provide a sealed enclosure within the cab for it.

 

[greenboy]

I'm not sure if this means much to this thread but I believe the Eminence Alpha 8MR is self contained - you don't need to provide a sealed enclosure within the cab for it.

Sure. That makes for cheaper and faster builds. But it comes with a penalty: sonic performance, sound quality. The open-back Ems sound better. So do the 18 Sound and B&C small-format midrange drivers.

 

[Stromrider]

Hey Stromrider,

Imaging, as in multiple sources with differing responses in close proximity operating partly in the same passband, as you have when a driver is stopping at 1K Hz while the other is starting at 200 Hz (or whatever).

I use asymmetrical SMS-driven crossovers too - but only to optimize actual response of the two drivers - not to get them both reproducing some of the same frequencies. Doing that smears the sound, and contributes some additional odd polar anomolies.

Ahhh... Now i get it, we have a misunderstanding.

What i mean't was i could i have the xo point between the two drivers as low as 200hz or as high as 1khz. I would not have the mid playing down to 200hz, and the 15" up to 1khz. That defeats the purpose of a crossover.

Sorry for the confusion...

 

[greenboy]

Well, I will say this, Strom - to my ears crossing over a little higher has a benefit beyond the obvious power distribution in a musical signal and how that affects power handling of a driver. Carrying the brunt of the first few (4 to 8) predominant electric bass overtones on the woofer really makes for a nice unified voice, and also seems to satisfy those who are accustomed to and like the sound of a old school vibe.

And if you choose a good woofer like the 3015LF or BMS 15N630, it isn't going to run out of excursion until thermal limits or after - so why not place the body of the tone all in one place?

 

[Stromrider]

Well, I will say this, Strom - to my ears crossing over a little higher has a benefit beyond the obvious power distribution in a musical signal and how that affects power handling of a driver. Carrying the brunt of the first few (4 to 8) predominant electric bass overtones on the woofer really makes for a nice unified voice, and also seems to satisfy those who are accustomed to and like the sound of a old school vibe.

And if you choose a good woofer like the 3015LF or BMS 15N630, it isn't going to run out of excursion until thermal limits or after - so why not place the body of the tone all in one place?

I can agree with that. I think i am looking for a more old-schoolish sound from a modernish cab, so one reason behind the 8" is I want the harmonic distortion of the upper midrange. If i were building a dedicated PA speaker, i would use a 6", or a Bill F. design.

Where are the off axis measurements of the Eminence 8"s that you have referenced to in other posts?

 

[greenboy]

Where are the off axis measurements of the Eminence 8"s that you have referenced to in other posts?

I've never seen one. In a time-honored tradition, I've just heard it, noticed it, and then read up on what it's caused by. In general, based on wavelength propogation on given cone sizes, smaller drivers reach higher before "beaming". Here's a rough guide to beaming limits, calc'd by dividing 1130 ft per second (speed of sound) by actual cone front:

speaker   beaming limit
 size "        Hz
-------   -------------
  18           903
  15          1052
  12          1335
  10          1658
   8          2105
   6          2672
   5          3316
   2          6840
   1         13680

 

[Stromrider]

Very rough guide. Never seen a 1" cone driver, but i can tell you 1" dome tweeters do not beam until 18-20khz, the better ones anyway.

When i'm building a stereo speaker system i examine the faults of each driver and try to design around them. Off axis response is a big concern because thats what ultimately gives you the "image" effect. But thats for reproducing a recorded and mastered recording.

I'm not really worried about alot of the things i normally would be if i was designing a loudspeaker or PA cabinet while I'm thinking about this bass cabinet. If i build it and i end up wanting a PA speaker instead of it, i'll redesign, rebuild, and admit defeat.

 

[synaesthesia]

I'll hold off on the compressor, and if i find i need to save a bit more money i can use the active xo i use in my stereo setup for the testing phase.

I'd stay off 18s. They can sound 'slow'.

Re: crossover and compressor. Unless you want a specific compression effect, all you may need is some limiting. In which case, you might go for a Driverack or equivalent, which offers speaker management, crossover, EQ, limiting in one box. And you can 'RTA' your rig and feed corrective EQ.

I am using a Driverack PA in my bass rig now, using something better for my PA so this can be more useful somewhere else...