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Old 9th March 2015, 07:50 PM   #1
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Default Chris661's PA system thread

So I decided I've started a few threads on here, but never really got anywhere. Here's a thread where I'll keep track of everything. It'll probably end up a bit like a blog, but discussion is more than welcome.

So far, I have a pair of old EV 15" Deltamax tops with EV DH1a HF units on HP64 horns, with Beyma 15P1200Nd subwoofer drivers as midbass units. Active crossover at ~1.1kHz. I also have a spare set of those Beyma drivers. Having read through Art Welter's compression driver shootout, I'm keen to use the DH1as, as they perform very well. They're stuck on a 2" exit, though - no way of converting them to 1.4" exit.

Below is a thread on what I've been doing so far.
Compression driver help please

I'd like to widen the dispersion on the HF units, build some subs, and figure out some top speakers that I can actually lift on to stands.


I think I'll go for a set of four (eventually) THAM15s for subs, as they appear to dig low enough for most stuff, while being fairly compact.

For tops, I think a 12" two-way will be okay, provided efficiency is good. My current cabinets are limited at SPL: I'm running a Behringer NU6000DSP (~1200w/ch) for the Beyma 15"s, and hit the limiters during anything bigger than a smallish gig. I suspect I'm simply asking too much of a 2-way system - the free-field low-frequency rolloff comes in around 45Hz, so efficiency is rather low. Groundplane subs would be a much better solution.

After a bit of looking around, I've found these:
RCF - MB12N251
They're available at a reasonable price, and allow the use of a ~40L cabinet tuned to around 80Hz for considerable SPL in the kick region. If anyone has suggestions for a different 12" driver, I'd be interested to find out - those RCFs are the top-end of what I'd want to spend (100/driver).


I might go for a modular top design, with the mids and HF units in seperate stackable cabinets, for MTM/TMM/TM tops, depending on the SPL needed. A modular design would also make it easy to expand the system later, and, of course make it easy to get those DH1as up high, possibly on a different horn.

I have lots of amplifiers on-hand, and a couple of active crossover/EQ units, so this will be active crossovers and measurements all the way. Preliminary crossover points would be ~1kHz between the DH1a and 12", and ~120Hz from subs to mids.

That's all for now, I'm gonna go make stir-fry.

Chris
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Old 11th March 2015, 09:42 AM   #2
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Take the 2" adaptor off the DH1A and you will have a 1.4" exit.

The blue Locktite EV uses makes removal of the three screws holding the DH1 adapter on difficult.
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Old 12th March 2015, 05:41 PM   #3
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Hi djk,

I removed one of the adapters, and the set of 4 mounting holes normally found on 1.4" exit drivers simply weren't there. I'm not prepared to drill these, as they're my best compression drivers.
Since its a pain to get the driver out of these cabinets, I didn't check the other one.

Click the image to open in full size.


In other news, I've been toying with the THAM15 design slightly in Hornresp - its possible to shove the rolloff down a few Hz by increasing the height a little, stretching the middle section. I'd like solid 40Hz output so that music such as Invaders Must Die (Prodigy) and Slam (Pendulum) have the bottom end they need.

Chris
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Old 12th March 2015, 09:26 PM   #4
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I should also add that I have a few coaxial stage monitors, 3x 8"s, and a pair of 12"s. Since the 12"s have decent power handling, I'm going to install some top-hat sockets on them, for use as the mid-high speakers in the setup described above.

Problem is, the frequency response is, quite literally, all over the show:
Click the image to open in full size.

I took a few measurements, and the positions of the peaks and dips move around a bit, but there's clearly something wrong here. An average looked awful, since the dips were almost complete cancellations at different frequencies/positions. The 8-10kHz haystack definitely needs fixing.
They were done with an ECM8000 close to the front grille, and didn't change much when I swapped the stock compression drivers for some Das Audio M3s (which are fairly nice), so there's clearly a problem with the coaxial horn. Removing the grille didn't change much IIRC.

I have some spare plastic 90x60 horns lying around, that load down to 1kHz, so I was thinking of hacking those down at the throat end to sit in the coaxial speakers, for proper horn loading rather than the short conical expansion that's currently there. Whittling to be done.

Chris
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Old 14th March 2015, 07:45 AM   #5
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"I'm not prepared to drill these,"

A 4mm aluminum plate could have studs on a standard 4" bolt circle for a standard 1.5" entry horn, and then run some flatheads thru the 4mm into the EV three-hole.

I wish shipping wasn't so dear to the UK, I probably have just what you want laying around.
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Old 14th March 2015, 04:04 PM   #6
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That's a thought.
A quick look on eBay shows I could get a pair of aluminium plates for 10. I don't think I'd be able to cut the central hole nicely, though - the exit angle needs to be exact.

Looks like I'm staying with the 2" exit for now, though - if I go modular, P.Audio sells a decent-looking 90x40 2" horn. I'd make sure that horn could be swapped with the EV one for long rooms.


I've been hacking away at one of these horns. Looks like I could use some plumber's putty or similar to get a nice smooth transition through the woofer. Hopefully that'll clear up the CD response somewhat.
I'll be starting by THAM15 builds in Summer - haven't quite decided on how much to modify the design by, if at all.

Chris
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Old 15th March 2015, 04:04 AM   #7
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It is a nice driver as is, but you should see if you can get it in the manifold version as it came with a 1.4" exit with four-bolt mounting (I have a pair on my desk as we speak).
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Old 16th March 2015, 07:30 PM   #8
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I'd love to, though EV parts are incredibly rare over here - I only got these DH1As because I did some work and got some Deltamax cabs and replaced the diaphrams myself.


Now I'm torn between THAM15s and some teeny tiny ported boxes:
Q15 Compact 15" Bass bin - Speakerplans.com Forums - Page 1
THAM15s will have way more output, but the ported boxes are much easier to move around and can be scaled for different-sized gigs.

Chris
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Old 21st March 2015, 01:17 PM   #9
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Finally got the mid-highs sorted.
I've ordered a pair of Fane Sovereign Pro 12-500 midbass drivers, and a pair of P.Audio 90x40 horns.
The Fanes will be going in some Tannoy i12 cabinets (got them cheap), with the compression drivers placed on top (and then bolted down). The Tannoy cabs might need some playing with the port tuning and EQ, but I'm confident I can get something good there.

I'll make two of the ports blockable, so I can drop the tuning down to ~60Hz and EQ the bass up for smaller gigs. The Fanes are 500w rated and have 6mm Xmax, so they'll do just fine. For bigger gigs, port tuning will be ~90Hz, and then EQ the peak down to get them flat, which means they'll have loads of power handling towards the cutoff.

Once everything has arrived, I'll be getting out the measurement mic and will post results.

The Deltamax cabinets will probably end up on eBay. They've not been kind to my speaker stands - I can't get them on stands by myself, but the above modular system ought to be nice and easy.

Chris
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Old 22nd March 2015, 04:14 AM   #10
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The Fane Sovereign Pro 12-500 looks like a great driver, glad you got things sorted out.
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