Hello everyone,
I recently built a horn which I'd like to cross over to at 700Hz, based on recommendations.
I have two pairs of Eminence Alpha 8as, and planned to build a box that matches the vented enclosure spec Eminence suggest.
However, having 4 drivers makes me wonder if:
I recently built a horn which I'd like to cross over to at 700Hz, based on recommendations.
I have two pairs of Eminence Alpha 8as, and planned to build a box that matches the vented enclosure spec Eminence suggest.
However, having 4 drivers makes me wonder if:
- Do I need 4 for indoor listening?
- How would I account for 2 drivers per box when the original vented design is for one driver?
Hi, the horn looks big! as it should to be to be able to play down to 700Hz. Is it multiple entry horn? Have you measured it already?
You should try and match the bass directivity to the horn to be able to crossover without too much issues on power response, mismatch in directivity. This means the two 8" should probably be side by side, or something like 15" driver might be better, just for the directivity match. The magic is try and crossover where the woofer is starting to beam and the horn is losing its pattern control.
You can crossover lower, where the horn has lost pattern control, as well as 8" doesn't yet beam (both have similar directivity, omni or close to omni) but usually this is too low for the driver in the horn and might sound bad especially with any SPL. Multiple entry horn could be fine, but for tweeters it would be at the very limits of capabilities.
SPL requirements for home use is different for all, but I think those who have capable systems wont go back to smaller so I suggest use both 8". I'd keep them closed and have one more way for lows, like subs or big woofer in the mains. 8" doesn't do too much bass. Enough for low volume listening, but the nice loud sweet listening level that puts smile on your face would benefit more cone area. This doesn't mean you have to play it loud, the dynamics stay good all the way.
If you add separate woofer keep the 8a in sealed box since then you don't need the bass boost for them the porting would provide. Only the lowest playing "way" in any system needs a port, extension to bass frequencies.
To come up with ported box for two drivers, check out WinISD or some online loudspeakerbox calculator and test what it suggests for 1 or 2 drivers. Box volume should double and port needs to be adjusted for the now doubled volume to keep tuning frequency the same. Ports scale unintuitively, bigger port area requires longer lenght to have same tuning frequency for a box!
Hope it helps
You should try and match the bass directivity to the horn to be able to crossover without too much issues on power response, mismatch in directivity. This means the two 8" should probably be side by side, or something like 15" driver might be better, just for the directivity match. The magic is try and crossover where the woofer is starting to beam and the horn is losing its pattern control.
You can crossover lower, where the horn has lost pattern control, as well as 8" doesn't yet beam (both have similar directivity, omni or close to omni) but usually this is too low for the driver in the horn and might sound bad especially with any SPL. Multiple entry horn could be fine, but for tweeters it would be at the very limits of capabilities.
SPL requirements for home use is different for all, but I think those who have capable systems wont go back to smaller so I suggest use both 8". I'd keep them closed and have one more way for lows, like subs or big woofer in the mains. 8" doesn't do too much bass. Enough for low volume listening, but the nice loud sweet listening level that puts smile on your face would benefit more cone area. This doesn't mean you have to play it loud, the dynamics stay good all the way.
If you add separate woofer keep the 8a in sealed box since then you don't need the bass boost for them the porting would provide. Only the lowest playing "way" in any system needs a port, extension to bass frequencies.
To come up with ported box for two drivers, check out WinISD or some online loudspeakerbox calculator and test what it suggests for 1 or 2 drivers. Box volume should double and port needs to be adjusted for the now doubled volume to keep tuning frequency the same. Ports scale unintuitively, bigger port area requires longer lenght to have same tuning frequency for a box!
Hope it helps
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Hi, the horn looks big! as it should to be to be able to play down to 700Hz. Is it multiple entry horn? Have you measured it already?
You should try and match the bass directivity to the horn to be able to crossover without too much issues on power response, mismatch in directivity. This means the two 8" should probably be side by side, or something like 15" driver might be better, just for the directivity match. The magic is try and crossover where the woofer is starting to beam and the horn is losing its pattern control.
You can crossover lower, where the horn has lost pattern control, as well as 8" doesn't yet beam (both have similar directivity, omni or close to omni) but usually this is too low for the driver in the horn and might sound bad especially with any SPL. Multiple entry horn could be fine, but for tweeters it would be at the very limits of capabilities.
SPL requirements for home use is different for all, but I think those who have capable systems wont go back to smaller so I suggest use both 8". I'd keep them closed and have one more way for lows, like subs or big woofer in the mains. 8" doesn't do too much bass. Enough for low volume listening, but the nice loud sweet listening level that puts smile on your face would benefit more cone area. This doesn't mean you have to play it loud, the dynamics stay good all the way.
If you add separate woofer keep the 8a in sealed box since then you don't need the bass boost for them the porting would provide. Only the lowest playing "way" in any system needs a port, extension to bass frequencies.
To come up with ported box for two drivers, check out WinISD or some online loudspeakerbox calculator and test what it suggests for 1 or 2 drivers. Box volume should double and port needs to be adjusted for the now doubled volume to keep tuning frequency the same. Ports scale unintuitively, bigger port area requires longer lenght to have same tuning frequency for a box!
Hope it helps
Thanks very much for your reply tmuikku! This is probably all of the information I need to get started
I haven't used WinISD for a while, so I started playing around with it again today. Two drivers definitely makes sense, based on what you've said here, and that's a really good point about using a sealed box. I do have subwoofers, so these only need to handle 160-700Hz (or wherever we decide to cross it over to the horn).
The horn is large, made from bwaslo's SynergyCalc spreadsheet, so I put in 250Hz as the lowest frequency the horn should maintain pattern control to. Joseph Crowe also made a horn that loads that planar driver down to 300Hz, so it's definitely got a flexible range to work with!
I can work with a sealed box
I appreciate the advice!Edit: After playing some more with WinISD, it looks like I can make a smaller vented box (54 litres, rather than 90). I know I don't need the low-end extension, but I'd like to use a smaller box if I can.
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Room response and box shape will make the response completely different in real life.
No need to sweat to many details in simulation.
WinIsd is just good for calculating alignments.
Theile Small theory was just based on matching the speaker response to a filter.
This case a basic 3rd order Butterworth or Quasi Butterworth = QB3 would be fine.
For your application the Alpha works fine in 28 to 35 liters per driver. So 56 to 70 liters for 2x drivers.
Since it will be high passed for midbass. Its likely sealed or ported would sound fine.
If your highpass is going to be around 60 to 80hz
then the port wont be doing much anyways.
I agree, simple sealed box is simple and more accurate
No need to sweat to many details in simulation.
WinIsd is just good for calculating alignments.
Theile Small theory was just based on matching the speaker response to a filter.
This case a basic 3rd order Butterworth or Quasi Butterworth = QB3 would be fine.
For your application the Alpha works fine in 28 to 35 liters per driver. So 56 to 70 liters for 2x drivers.
Since it will be high passed for midbass. Its likely sealed or ported would sound fine.
If your highpass is going to be around 60 to 80hz
then the port wont be doing much anyways.
I agree, simple sealed box is simple and more accurate
At this stage, I'm alright with simple
Regarding the front baffle, is there any benefit to angling the two drivers towards each other (in a slight V configuration), rather than flat?
I've seen v-coupling of subs, and curved centre array speakers, but I can't say I've seen it for midbass applications. That doesn't stop me from wondering though
Is there a different crossover frequency that comes to mind Allen? I'm certainly open to suggestions!
Yes, you pick a focal point where you want them to combine as one over a wide BW with the understanding that the front/back field isn't very deep. Can't recall any brands ATM, but there's been some studio monitors with very wide BW [mid] bass woofers XO'd to horns @ ~ 1 - 1.6 kHz IIRC.
Way back when I was messing with arrays I preferred the concave one best overall with the late '70s era Sony mobile audio 6.5" coax that also made above average inexpensive ~ 'full range' bookshelf speakers or my preferred tower alignments [MLTLs in today's parlance]. Anyway, too much 'head in vice' for us, so definitely would need much smaller drivers and/or a longer focal point.
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.........as in dual vertical 8" = ~700 Hz @ 90 deg, ergo ~1400 Hz/90 deg horizontally or...... ?
The crossover point could be a number of things, there may be a range of possible crossing where it is possible but with varying pros and cons. Also, crossing a waveguide that is not round or square adds an extra layer of complexity.
Normally I'd not try to guess something like this. I'd take (at least) a series of polar measurements, both horizontal and vertical, both horn and woofer pair as the minimum to work this out.
However if OP has another method in mind then we could throw in some guesses.
Normally I'd not try to guess something like this. I'd take (at least) a series of polar measurements, both horizontal and vertical, both horn and woofer pair as the minimum to work this out.
However if OP has another method in mind then we could throw in some guesses.
Sorry for the delay. Happy holidays everyone!
I have a plot (1/12 octave smoothing) with the calibrated mic (though I haven't calibrated the output stage of REW yet), but I thought I'd post this in case there were days between then and now
I set the sweep from 150Hz-20kHz. Hopefully this helps! The mic is at 0 degrees, 1m away. The SPL level that REW detected was 80dB (I didn't want to go too loud and wake the kids up).
I have a plot (1/12 octave smoothing) with the calibrated mic (though I haven't calibrated the output stage of REW yet), but I thought I'd post this in case there were days between then and now
I set the sweep from 150Hz-20kHz. Hopefully this helps! The mic is at 0 degrees, 1m away. The SPL level that REW detected was 80dB (I didn't want to go too loud and wake the kids up).
Attachments
Ok, here's a second measurement (green) where I've included the noise floor in the plot (red) (I measured in a different room because I was tired of being cold
).This is also a full sweep rather than starting at 150Hz.
Attachments
Happy New Year! I managed to sneak in a few minutes to take some horizontal measurements of the horn (see attached). I'll attempt to add the vertical measurements as soon as I can.
The measurements were taken in 5 degree increments, starting at 0 degrees (directly in front of the speaker), going around to 90 degrees at the end. I can provide the mdat file from REW if anyone wants it, but it's too large to attach to this post
The measurements were taken in 5 degree increments, starting at 0 degrees (directly in front of the speaker), going around to 90 degrees at the end. I can provide the mdat file from REW if anyone wants it, but it's too large to attach to this post
