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Old 20th October 2013, 07:25 PM   #1
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Default Synergy with BMS 4550, Visaton M10 and ...

After trying to gather as much info on the Synergy horn topic as I could, I'm now trying to put it all together into a new project, meant to be coupled with the sub I built here.
After watching and listening to various Youtube videos, it had to be a Synergy horn design . But it is not so straightforward to design one, as you all probably know.

I'm shooting for 130dB SPL, as the speaker is meant to complement the sub and the whole system is to be used with an electric drum set, and must be suitable to play gigs with.

The BMS 4550 compression drivers seemed a sure thing, since they're used in several Tom Danley designs. So for the top end I'm decided on this driver (already bought 2). For mids, looking at availability, I'm not going to get my hands on the Celestion TF0410MR's, so when the Visaton M10 popped up as a usable driver, I happily chose this one for starters.

I haven't decided on woofers yet. I did some quick simulations in Hornresp, but since I started top down, my first objective was to get the mids done correctly/according to my needs.

Transport-wise there are some restrictions to the cabinets: I need to be able to place them in the aforementioned sub if I want to be able to put it all in my car. So dimension-wise, I'm limited to WxHxD=80x48x50 cm (or 31.5x18.9x19.7 inch).

So here's what I think should work:
1 BMS 4550,
4 Visaton M10s,
2 10" or 12" woofer, tbd,
in a 70x30 degree Synergy horn.

I'm using bwaslo's Spreadsheet (many thanks!):
Click the image to open in full size.

I'm shooting for a tweeter-mid crossover @ 1000Hz and mid-woofer crossover @ 300Hz. Adding the path length of the BMS (6.7cm) and subtracting a throat adapter of 1.5cm, Con12 works out to 13.33... (am I doing this correctly? )
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This results in the following response:
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...with a phase response of:
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Calculating max SPL:
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...and the corresponding particle velocity at the mid ports:
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Now this last one worries me . With all the graphs I've seen so far, particle velocity is largest in the lower frequencies, so what the f is going on here . This is where I'm stuck at the moment, asking myself whether this design will do what it needs to. I'll probably be pushing some parameters around, hoping to find better results, but if anyone wnats to chip in, please do so . I'm eager to learn.
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Old 20th October 2013, 09:43 PM   #2
JLH is offline JLH  United States
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125dB is considered by many to be the onset of pain. Why do you need 130dB? You need big mid entry ports to get anywhere near 130dB.
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Old 20th October 2013, 09:59 PM   #3
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Hmm, I already spotted some mistakes... When calculating for maximum SPL, Hornresp seems to ask for the maximum power per speaker, not for maximum total power . So here are the corrected graphs:

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Now it seems there is no problem, since the generally accepted limit of 17 m/s is never reached, not even close.

SPL is at 127dB peak with 100W going into each mid unit, so two horns should be able to do 130dB easily, with 3dB headroom. As far as my head calculations go, that's half of the max power @130dB, so 50W/speaker, or 200W total power per box for the mids.

Looks like it's a green light for the first proto .

The only thing that bothers me a little, is the dip around 700Hz... that corresponds to almost exactly double the length of the whole horn. Could it be some 1/2 wavelength cancellation 'notch'?
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Old 20th October 2013, 10:10 PM   #4
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Quote:
Originally Posted by JLH View Post
125dB is considered by many to be the onset of pain. Why do you need 130dB? You need big mid entry ports to get anywhere near 130dB.
Well, honestly, I thought the pain limit was at 120dB, but anyway...

I trust you have heard a snare drum sometime 'in real life'. I have not measured the peak SPL of my snare drum, but I would say it's not that hard to hit it and make you ears hurt. Suffice it to say I looooveeee my ear protection buds when I'm playing .
So in order to be able to produce a 'live sound feel', I'd prefer to be sure I have the headroom available, if needed.

In the sub-build thread I elaborate on my idea for this set. In short: I'd like to use an edrum set coupled to software like Toontrack Superior Drummer or Addictive Drums for live gigs, instead of an acoustic set. The pros: way better sound, easily adjustable and controllable. The cons: there's no such thing on the market, I have to do it from scratch. But that's part of the fun .

[edit]
Oh, and the SH50 does 130dB, so it should be feasible .

Last edited by Thijs666; 20th October 2013 at 10:13 PM.
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Old 20th October 2013, 10:51 PM   #5
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I think you're going to have trouble getting rid of that strong output above 1kHz unless you use a very high order crossover.
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Old 21st October 2013, 12:59 AM   #6
JLH is offline JLH  United States
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Quote:
Originally Posted by bwaslo View Post
I think you're going to have trouble getting rid of that strong output above 1kHz unless you use a very high order crossover.
That's a good observation. However, Hornresponse sometimes calculates the peaks to be higher than what they measure in real life. I would still move ahead with the build and measure it to see if the peaks are really that high. If they are, then you can increase the front mid chamber volume to act as a more effective low pass filter.
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Old 21st October 2013, 04:42 PM   #7
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Quote:
Originally Posted by bwaslo View Post
I think you're going to have trouble getting rid of that strong output above 1kHz unless you use a very high order crossover.
Quote:
Originally Posted by JLH View Post
That's a good observation. However, Hornresponse sometimes calculates the peaks to be higher than what they measure in real life. I would still move ahead with the build and measure it to see if the peaks are really that high. If they are, then you can increase the front mid chamber volume to act as a more effective low pass filter.
Thanks for the heads up. I already simmed an active crossover 8th order@1000Hz, which dropped the bump 20dB below average.

I also simmed a bigger Vtc, but that barely gave any (good) results. A smaller Vtc however, seemed to push the out-of-band bump down a little .

I think I'll just start a proto and measure. But first I have to figure out if the mids will fit physically in the horn .

Just to be sure: the Conxx length is measured through the center of the horn, not alongside the horn sides, is it? (it would result in two different path lengths if it would be measured alongside the horn sides, but I'm still asking just so I don't err here).
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Old 22nd October 2013, 07:42 PM   #8
JLH is offline JLH  United States
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Its down the center axis of the horn.
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Old 24th October 2013, 09:09 PM   #9
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Originally Posted by JLH View Post
Its down the center axis of the horn.
Thanks!.

It turned out placing the drivers was impossible, the mid ports were too far apart in the horn top and bottom. So it was back to the drawing board...

... and this is what came out .

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I switched to 6 drivers, because of the relatively low efficiency of the M10's.

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Muuuccchhh better

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Particle velocity looks fine...

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No problems here either...

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And even the impulse response looks acceptible (at least to my eyes).

Click the image to open in full size..

Would you say this is worth trying?

ok, I admit, I still have to (try to) lay it out on the horn, but it looks doable
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Old 25th October 2013, 04:13 PM   #10
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Hmm, it's going to be tricky, but I think it'll work...

Click the image to open in full size.


I had a look at the Eminence Delta-12LFA for the woofer part. The sims turn out great with two of them! I feel I'm in luck . Unless someone discovers a flaw in my sims . Here's some graphs:

Click the image to open in full size.
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Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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