Hi everyone, I’m really excited to be part of this community, I’ve learned so much already just by reading all these informative posts.
I’m in the middle of a build based on the Eminence Beta-8CX and ASD:1001 that you might find interesting, but I’m in the weeds with it a bit at the moment.
The design is a little unconventional—it’s actually a guitar cabinet that uses one traditional guitar speaker and a pair of Beta-8CX in what’s called a “wet/dry/wet” configuration
A picture is worth a thousand words, so maybe this communicates the idea better…
The 12” guitar speaker is powered by a traditional tube guitar amplifier and the Beta-8CX/ASD:1001s are powered by a miniDSP plate amp.
In this type of system, the tube amp and guitar speaker only amplify the dry guitar sound, while the stereo speakers amplify the effected “wet” signal.
This configuration allows for the cleanest possibly reproduction of time-based stereo effects like delay and reverb.
For those that follow this side of the music tech world, “FRFR” (or full-range, flat response) speakers have become trendy as a way to use digital amp modeling technology live on stage.
FRFR is also a natural choice for effects like delay and reverb that need much more high end than a guitar speaker can traditionally deliver.
I was inspired to create this design by several companies that use the Beta- *CX/ASD:1001 combo with pre-built plate amps in their FRFR products.
In my build the coaxial speakers are housed inside ported sub-enclosures built into the overall structure of the cabinet. The dimensions of these are based on measurements from the DIY audio speaker volume calculator.
Here’s what the rear of the cabinet looks like:
I’ll admit the build quality is pretty sloppy, but this was just intended to be a prototype. In any case...it’s not performing very well.
The guitar speaker sounds fine, but the hi-fi speakers are off. They’re thin and brittle yet somehow also boomy and congested in the lower mids at the same time.
I used a measurement mic to try correcting the response of the coaxial speakers with the DSP and that helped, but I still suspect something is very wrong.
I’m looking to totally redesign the cabinet for the next prototype and I really want to get it right this time!
I’m not really sure how to reach out for help on this, but I hope this project is interesting enough for some experienced members to offer their input on how I could improve the performance of the hi-fi speakers.
Thanks for any and all feedback on this build!
I’m in the middle of a build based on the Eminence Beta-8CX and ASD:1001 that you might find interesting, but I’m in the weeds with it a bit at the moment.
The design is a little unconventional—it’s actually a guitar cabinet that uses one traditional guitar speaker and a pair of Beta-8CX in what’s called a “wet/dry/wet” configuration
A picture is worth a thousand words, so maybe this communicates the idea better…
An externally hosted image should be here but it was not working when we last tested it.
The 12” guitar speaker is powered by a traditional tube guitar amplifier and the Beta-8CX/ASD:1001s are powered by a miniDSP plate amp.
In this type of system, the tube amp and guitar speaker only amplify the dry guitar sound, while the stereo speakers amplify the effected “wet” signal.
This configuration allows for the cleanest possibly reproduction of time-based stereo effects like delay and reverb.
For those that follow this side of the music tech world, “FRFR” (or full-range, flat response) speakers have become trendy as a way to use digital amp modeling technology live on stage.
FRFR is also a natural choice for effects like delay and reverb that need much more high end than a guitar speaker can traditionally deliver.
I was inspired to create this design by several companies that use the Beta- *CX/ASD:1001 combo with pre-built plate amps in their FRFR products.
In my build the coaxial speakers are housed inside ported sub-enclosures built into the overall structure of the cabinet. The dimensions of these are based on measurements from the DIY audio speaker volume calculator.
Here’s what the rear of the cabinet looks like:
An externally hosted image should be here but it was not working when we last tested it.
I’ll admit the build quality is pretty sloppy, but this was just intended to be a prototype. In any case...it’s not performing very well.
The guitar speaker sounds fine, but the hi-fi speakers are off. They’re thin and brittle yet somehow also boomy and congested in the lower mids at the same time.
I used a measurement mic to try correcting the response of the coaxial speakers with the DSP and that helped, but I still suspect something is very wrong.
I’m looking to totally redesign the cabinet for the next prototype and I really want to get it right this time!
I’m not really sure how to reach out for help on this, but I hope this project is interesting enough for some experienced members to offer their input on how I could improve the performance of the hi-fi speakers.
Thanks for any and all feedback on this build!
Interesting thread, especially for me.
Here is why.
I have recently build quite a few projects based on guitar amp inspiration but with FRFR in mind for home/studio use (not guitar amp, but dual stereo).
The projects have included dual 15” fane full range drivers, single 12” again fane full range, and more recently Eminence beta 12 and 10” coaxials.
I’m still working the 10”.
My next project will be the 8” you have here in a three way design with 15” sub.
My initial questions to you is:
- what is your crossover?
- what is your amp specs?
- why open back for the 12”?
- what’s the volume and bass reflex spec for the 8”?
- any damping used?
I don’t know much about guitar amps and to what degree it can be used for hifi but with a flat response I think you have a small 2.1 boombox concept going on here.
I think the first error here is the bass reflex pointing upwards into the box.
Secondly I think I would’ve made two similar sized boxes instead: one for the 12”, another for the two 8”. Gives you more flexibility for future and more volume for bass on the 8 making it closed back.
Here is why.
I have recently build quite a few projects based on guitar amp inspiration but with FRFR in mind for home/studio use (not guitar amp, but dual stereo).
The projects have included dual 15” fane full range drivers, single 12” again fane full range, and more recently Eminence beta 12 and 10” coaxials.
I’m still working the 10”.
My next project will be the 8” you have here in a three way design with 15” sub.
My initial questions to you is:
- what is your crossover?
- what is your amp specs?
- why open back for the 12”?
- what’s the volume and bass reflex spec for the 8”?
- any damping used?
I don’t know much about guitar amps and to what degree it can be used for hifi but with a flat response I think you have a small 2.1 boombox concept going on here.
I think the first error here is the bass reflex pointing upwards into the box.
Secondly I think I would’ve made two similar sized boxes instead: one for the 12”, another for the two 8”. Gives you more flexibility for future and more volume for bass on the 8 making it closed back.
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interesting build. i have no idea what you are trying to achieve but it looks to me it can be a bit messy, since you have measurements, how does each driver measure?
I used the Eminence PXB2:2K5CX crossover which seemed to be recommended for the Beta-CX and ASD:1001 combo, but in the future I would consider an active crossover and bi-amp setup. I've heard some FRFR designers claim that custom crossover points are essential for a convincingly flat response.
The amp is the miniDSP PWR-ICE250 plate amp which seems to work great, with plenty of headroom for the application. Instead of bi-amping I'm using a single unit with the passive crossovers to get two channels for stereo—it was a bit cheaper this way.
For guitar, I'm probably in the minority that prefer open back cabinets, especially for AlNiCo Speakers like the Celestion Gold that's mounted in there now.
As for the enclosure volume and bass reflex, here's what I punched into the calculator:
An externally hosted image should be here but it was not working when we last tested it.
I figured it would get me somewhere in the ballpark of Eminence's published enclosure design for the Beta-8CX
I did use some damping—I chose the 3/4" acoustic sound damping foam from Parts-Express, largely because it was getting quite crowded inside the enclosures. My gut feeling is that I just made them way too small.
I wondered about that and I'm sure it's part of the problem—thanks.
With larger guitar speakers, things like rear mounting, the proximity to the edge of the cabinet baffle and floor are no big deal, the diffraction and resonance caused by those sharp edges and a 3/4" deep duct around the speaker surround add "character".
Flush mounting the co-ax drivers would reduce some of the peaks and dips caused by the above.
Mounting the co-ax drivers at the top of the cabinet (flipping the cabinet over) and directing it at your ears would help the upper response clarity. The on axis response of the drivers are fairly rough to start with, the off-axis response is probably worse. The fixed center to center distance of the co-ax also presents comb-filter problems between the pair and the 12", compounded by the time delay (around 1.75 ms latency IIRC) inherent in the DSP, even before the additional latency added by any digital effects processors.
That said, I suspect those issues may still be small compared to the polar response of the open back speaker combined with the pair of the ported speakers. Try sealing the back of the cabinet and see if that clears up the boomy and congested sound.
Edit: the ports in their present position are not a problem, but if the back of the 12" is sealed, their exits would have to be moved to the front or sides of the cabinet to be useful.
That said, having built a dual Alpha 8 ported guitar cabinet with port tuning options, I preferred the sound of it sealed.
What is the Fb (box tuning frequency) for the 8" ported cabinets?
Art
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that's a cool and well made cabinet. 2K5CX's 2mH/10uF lowpass might muddy things up somewhat. (?)
Could the rear cavity be acting with port output to bump things up in the 100-200Hz range?
Eminence's old "generic" 3K5 network used around 1mH and maybe 10uF (?) that gave ~2K8 crossover with Beta8cx
and APT50
Rkondra used the following - like 0.5mH. and a 15uF/8R Zobel. (am not sure what his notch filter is supposed to oo - ?)
Could the rear cavity be acting with port output to bump things up in the 100-200Hz range?
Eminence's old "generic" 3K5 network used around 1mH and maybe 10uF (?) that gave ~2K8 crossover with Beta8cx
and APT50
Rkondra used the following - like 0.5mH. and a 15uF/8R Zobel. (am not sure what his notch filter is supposed to oo - ?)
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I use Eminence PXB2:2K5CX myself with the 10" and 12" with decent results, not perfect but very warm and smooth but with some lacking mids around xo point. With a different HF CD you could also lower the xo point some and have a steeper and somewhat higher LF slope allowing more mids. But I think I would separate the two sections into separate cabinets, making the betas run with bassreflex in front same volume as the 12" example 40*60cm inner baffle and 30cm inner depth giving aprox 70l for the two 8". But for guitar use I really have no idea, all my advice is from hifi/2.1 perspective assuming the 12" is used as sub, which I understand is not the case at all in your application.
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Hi everyone, thanks for all the insightful commentary on this thread—I just got a chance to make a detailed reply so thanks for bearing with me!
There's a lot of good points here so I'll try to respond to everything.
freddi,
I think my next experiment might be to reconfigure my PWR-ICE250 temporarily as a single channel bi-amp to test crossover points.
weltersys,
celef,
Lastly, if anyone isn't familiar with the concept of wet/dry/wet rigs in general, here's an in-depth video that explains it really well.
Evolution of Wet/Dry/Wet: 80s, 90s, & Now - YouTube
There's a lot of good points here so I'll try to respond to everything.
freddi,
I hadn't considered this but it makes a ton of sense, especially if that crossover is used more commonly with the 10" and 12" Beta-CX.
I think my next experiment might be to reconfigure my PWR-ICE250 temporarily as a single channel bi-amp to test crossover points.
weltersys,
This is definitely my first port of call for the next prototype. I've been using the cabinet mounted slightly off the ground and this seems to help for the clarity issues.
I was worried about this and I suspect that there is some comb filtering between the dry speaker and the coax boxes, but there isn't too much cancellation when the effects signal is 100% wet. At most, the latency amounts to a couple of extra ms of pre-delay on the reverb for example.
I hadn't considered this either and it seems like the most probable culprit to my gut instinct. When I go back to the drawing board I might try building a pair of freestanding cabinets at the dimensions I intend for the box interior and see if I can get those to sound a bit flatter.
I suppose I'll have to calculate that with some software? I'm planning to pick up the Eminence Designer app soon so maybe I can use that.
celef,
I know I have these somewhere, I'll try to dig them up this afternoon. One issue that might arise from this is that I decided not to buy the recommended miniDSP measurement mic because I had a Presonus PRM-1 lying around. Unfortunately, this mic does not ship with a calibration file so I'm not incredibly confident in the results. I'll probably buy a UMIK-2 for the next build.
Lastly, if anyone isn't familiar with the concept of wet/dry/wet rigs in general, here's an in-depth video that explains it really well.
Evolution of Wet/Dry/Wet: 80s, 90s, & Now - YouTube