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Old 9th July 2008, 04:22 AM   #1
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Default bms 4540ND buildup?

I want to make something out of my two unused 4540ND from bms.I have some cash and I need a summer activity!
Is there anyone out there that have made anything sucessfull out of my fridgemagnets?
Id love to add another big set of amazing speakers to the stable.
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H.Honda Chico CA Land of the fooled
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Old 9th July 2008, 06:24 AM   #2
BHTX is offline BHTX  United States
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I believe a handful of people have had great success with that driver on the DDS ENG 1-90 Pro waveguide. Crossover above about 1.6 KHz. Pair that with an adequate 10 or 12 inch midbass in a sealed chamber (10" would probably mate better with the waveguide, but won't go as low). Mate that with a 15" woofer like the Peavey Low Rider (great value btw) in about 4.75 cubes vented at 30 Hz. Lowpass the woofer at around 150-250 Hz, depending on the midbass. If you can obtain enough low frequency output to match that, the tuning above can work with a 40Hz highpass (like on most av receivers/preamp processors), and you should have a great sounding system, with TONS of headroom.. well over 120dB per channel in room, depending on your mid driver etc. Of course, this is all assuming a 4th order electronic with multiple amplifiers, since I still can't design a passive xo worth a flip.
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Old 10th July 2008, 12:54 AM   #3
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Thank you sir I will lookup that waveguide as that is something I had in mind..
I might go for a smaller 2way than you suggested with maybe a phl or other high quality 12 inch woofer.
Maybe even a 10inch.
Any Ideas anyyone?
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Old 10th July 2008, 04:37 AM   #4
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hello holger honda,

i just finished building some wooden smith horns today with the jbl 2407h (same as the bms), kinda like these:

http://audioheritage.org/vbulletin/s...ad.php?t=21202

i built mine closer in size to the smaller westlake horns, as I'm using them above 3 kHz. i threw a simple crossover on them and had a listen tonight and wow! compared to a few different plastic waveguides i've tried, the wood horns are much sweeter and very natural sounding. anyways, if you're handy with woodworking it could be a fun summer project.
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Old 12th July 2008, 12:34 AM   #5
Sjef is offline Sjef  Netherlands
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I have a pair of BMS 4540ND as well and use them on and off in my system depending on my mood. I have tried them with the popular 18Sound XT1464 and the 18Sound xt1086, both where quite horrible in combination with the BMS, can't recommend them. In the end I had let me made some 16 cm custom wooden waveguides a la Geddes design wich turned out to be pretty good from 3kHz upwards. I don't know the DDS waveguide but I suppose it's a lot better if you want to cross lower than I did.

Anyways, I wrote about it before but the BMS driver sound quite horrible when not properly driven in. I also made some very easy to do, virtually no cost but highly recommendable improvenement to the drivers themselves. The phaseplug of the 4540ND is made of hollow pastic. Mount them to a horn or waveguide and then tap your finger at the back of the driver and listen to the sound coming out of the horn, just plain horrible. Now imagine that ALL of the sound coming out of this driver is reflected by this phaseplug. When I just had these drivers they had a very annoying sqeeuck in their sound, ITS THE PHASEPLUG. I just ripped of the BMS logo on the back and filled the hollow phase plug completely with epoxy glue. After that I applied some tiny pieces off bitumen damping on the back. If I now tap my fingers on the back there's just a very dry "tapping fingers on the back sound" coming out of the horn without any annoying sounds anymore. Net result is that the driver sound much cleaner.

Second part is about burning in. These drivers are designed for very very high sound levels. Breaking in at home audio volumes is gonna take forever with these. After about 200 hours on them I had the feeling that they where not even for about 25% burned in, stiil a bit harsh and missing finesse. So what i did is very simple, I gave them Hell. Just let them play Mozart and Rammstein at the same time for days at levels at wich your ears start to bleed. Well actually I have put them in a damped box taped face to face and put on some pink noise at insane high levels and let them heat up like that for four days continuous, in other words just let them do excactly what they where designed for in the first place. Well that made a hell of a difference with these drivers. Suddenly all of the sqeeuckiness has gone with the wind, I can't recommend it too highly. Both tricks cost about nothing at all, and there is even no "hifi" voodoo involved. Oh yeah, and removing the bug screen also helped out a little, yuo don't need it for home use anyway.
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Old 17th July 2008, 02:57 AM   #6
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So it seems that the right horn is key with theese drivers.
I guess my next question is about diy waveguides for a threaded 1 inch......
Are there any plans out there for me so I dont have to do all the trial and error myself?
Thankful and hopeful.
If it all becomes a giant mess I have some fridgemagnets for sale.
They are real basdass and you can have photos of your extended family between the magnets and the fridge!
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Old 17th July 2008, 03:50 AM   #7
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For what it's worth, I too tried the BMS 4540ND (a threaded driver) with the XT1086 (a bolt-on waveguide) and some P-audio throat adapters. The measured response was pretty bad. I'm now using the BMS 4538 (a bolt-on driver), and the results are much better.

Everyone says that the driver-horn matching at the throat is important, and I saw the effect of poor throat matching with the 4540ND/XT1086 combination. With the throat adapters I used, there was a slight gap between the end of the driver and the end of the waveguide. I've heard other reports with other throat adapters that had a similar gap. I tried stuffing that gap with fish filter foam, and that helped a bit, but the effects of that resonance were still present.

Click the image to open in full size.

Black = without foam, blue = with foam.

In contrast, the 4538 works much better. The throat matching isn't perfect, I can feel a slight ridge where the ends of the driver and waveguide don't line up exactly. But you can see the improvement in the response (the upper set of curves is the tweeter):

Click the image to open in full size.

All curves are unsmoothed, the 4538 was measured outside with a longer gate. Ignore the ripples, those are probably reflections off my less-than-ideal mic stand.

My suggestion would be to stay away from bolt-on waveguides if you want to use this driver.
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Old 17th July 2008, 05:00 AM   #8
ttan98 is offline ttan98  Australia
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Hi,

I understand this is a BMS 4540ND thread, those who intending to buy new compression driver and matching horn should consider this combo,

DE250($110) and RCF horn, model:H100($28), taken with no baffle and no equalization. I believe this combo offers good value and sounds excellent. Horizontal and vertical FR curves not taken.

see Attachment for on-axis measurement.
Attached Images
File Type: jpg hempcone&d250h100&d220econo.jpg (90.3 KB, 1065 views)
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Old 17th July 2008, 10:18 AM   #9
Sjef is offline Sjef  Netherlands
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The RCF H100 is a real horn, not a waveguide. With real horns you do not get the decreasing response towards higher frequencies because they provide a boost in this area. That's the major difference between horns and waveguides. With horns you don't need a correction network and they are therefore much easier to implement.

I have tried several horns with the BMS driver and other compression drivers as well. What I end up nitliking about them is their depth. The H100 has a depth of 133mm for example wich in my experience is one of the reasons why the horizontal and vertical dispersion is very narrow at high frequencies wich leads to a typical "horn" sound. For that reason I always ended up with the use of a seperate supertweeter above 10kHz when using horns, something I was trying to avoid with the BMS driver.

In my case I'm using them on a open baffle arrangement so I wanted more dispersion and less horn depth. I have looked the entire planet for a good small waveguide a la geddes design with 100 to 110 degree dispersion and small overall diameter so it would be not so deep. I ended up with some custom made wooden waveguides with 105 degrees angle, bigger would not work because of the characteristics of the driver, in other words it would not be working as a proper waveguide anymore.
The waveguides are only 16cm in diameter and has a total depth including the roundover of only 55mm. It's effective from about 2,5kHz on up. This would not work well with shallow filter because you will always end up near it's cut-off frequency. I can get away with it because I'm using it from 3500Hz on up with 60db/oct filtering. All in all this is a special purpose design wich worked out pretty good. For general purpose, that is lower crossover frequencies and/or shallower filter types (well shallower then 60db/oct) I think the DDS waveguide works better, at least much better than the 18sound horn/guides and as long you live in America they are rather cheap as well.

By the way, the DE250 is a very nice driver indeed and as far as the little BMS driver is concerned I couldn't come up with a much better fridge magnet than these as well.
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Old 17th July 2008, 12:13 PM   #10
BHTX is offline BHTX  United States
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Great posts. Informative.

I have no experience with the DDS ENG 1-90 myself, but would certainly like to try it still. However, I've also been aware that there were some serious issues with these waveguides in regards to build quality.. I mean to a ridiculous point to where it didn't even seem usable in some cases. If I remember correctly, it might have only been certain waveguides from usspeaker or something like that. Here's a link to a thread on HTGuide with some info. IIRC, there's a bit of talk here and there throughout the entire thread in regards to this issue. Down the 2nd page, John_E_Janowitz posted a few good photos as well, so be sure not to miss those too if this is of any interest to you..

http://www.htguide.com/forum/showthr...8&page=1&pp=35

Mainly, I'd really like some reassurance as to what my waveguides are really going to look like when they arrive at my door, if I were to purchase a pair (or more), as I've been interested in these for several months now. The only thing that's kept me from trying them is the mixed comments I keep finding. However, one observation that seems pretty consistent throughout (although there's still not all that much really), is that they supposedly sound very good, as long as you get a decent set.

I know I had recommended these earlier myself, but I'd some how forgotten all about this potential issue at the time.
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