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Comp Upgrade: B&C DE250 or BMS 4540ND?
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Timebomb View Drop Down
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Points: 2716 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 1:49pm
The Celestion aluminium horns are not the best IMO, never really liked ali horns, they ring.   That one has a fast flare rate so not great for crossing lower, i find the 1745 fine crossed at 2.4KHz on the B&C ME10, any lower and it starts to sound harsh, this is the limit of the driver though as it is the same on larger horns.   If you are EQing out at 2.5KHz then your real crossover point may be as high as 3KHz. 

I havent got the 4524 but i have a few other BMS units and have been impressed with them, they need the right horn though, Steve is right look for a horn with a cutoff about an octave below your crossover point.  I am currently building some 208Hz 60x40 conical horns for my BMS 4595 for a 400Hz crossover point, the chipboard prototype sounds great.  
James Secker          facebook.com/soundgearuk
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levyte357 View Drop Down
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Points: 11743 		Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 1:50pm
Originally posted by Tony Wilkes Tony Wilkes wrote:

4540 is a screw fixing, the BMS  equivalent of the DE250 is the 4538. Either this or the B&C will be an improvement on the 1745's. The 1745 is not a bad comp it just seems to break-up early.


Originally posted by Moo Moo wrote:

I have a pair of concentric High mid horns with Celestion CDX1-1745 Comps.
They are currently in the celestion 180mm horns with the rubber inserts.

They are passively crossed at 2k, which is slightly lower than recommended by celestion, and I am hearing a nasty bit of distortion / honk at 2.5k which I usually have to EQ out.


I could take your CDX1 1745s as part ex against brand new DE250s. Wink

Let me know ASAP.



Edited by levyte357 - 23 February 2012 at 1:52pm
"Who am I? I'm the guy who does his job.. You must be the other guy".
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MarjanM View Drop Down
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Originally posted by Timebomb Timebomb wrote:

The Celestion aluminium horns are not the best IMO, never really liked ali horns, they ring.   That one has a fast flare rate so not great for crossing lower, i find the 1745 fine crossed at 2.4KHz on the B&C ME10, any lower and it starts to sound harsh, this is the limit of the driver though as it is the same on larger horns.   If you are EQing out at 2.5KHz then your real crossover point may be as high as 3KHz. 

I havent got the 4524 but i have a few other BMS units and have been impressed with them, they need the right horn though, Steve is right look for a horn with a cutoff about an octave below your crossover point.  I am currently building some 208Hz 60x40 conical horns for my BMS 4595 for a 400Hz crossover point, the chipboard prototype sounds great.  

I would really like to see some of that work. Can you share some more info please?
Marjan Milosevic
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Timebomb View Drop Down
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Points: 2716 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 8:15pm
Its a linear horn 400mm Deep 60x40 degree side walls, ill take some pictures when iv finished them.
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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MarjanM View Drop Down
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Points: 7816 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:30pm
You mean just a straight horn?
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Moo View Drop Down
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Points: 21 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Moo Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:55pm
Wow.
Thanks everyone for your comments. Its going to take me a while to digest that lot.

My Mid Top cabs are concentric, which means that the HF Horn is in free space in the centre of the exit of the Mid horn Similar to a D&B C7. The celestion H1-7050 horn I currently use is 180x180, I would not want to go much bigger because it will obscure more of the mouth of the mid horn. 
From what you are saying I need the HF to be able to play down to 1k to crossover at 2k and avoid a prominent mouth reflection resonance.

I also need to get out and measure both the HF and LF sections separately to be sure that the breakup I am hearing at 2.5k is coming from the HF and not the top end of LF.

I am now confused about which of the BMS comps and which horn would be the best match for me.

I have always been confused about how to match the power rating of the Comp Vs Mid driver. My mid driver is the eminence Delta Pro 12 400w on a horn which makes it about 105db. My current comps are rated 75w and 110db. I have managed to blow one when I made a silly mistake, but would not want to go with a lower powered comp and keep blowing them in general use. 
Is there a general rule of thumb for matching LF and HF driver power ratios?
I always use a Driverack in the system so 113db comps would not be a problem, and would give me more headroom. I would like to Bi-amp the tops, but my back is twitching at the thought of lifting another amp every saturday.

Tony: I have read that it is critical to get a good match in the exit angle of the comp to the horn to avoid a cavity resonance in the join area. Is the Faital STH100 a good match for the exit angle on the BMS comps? Also is the Faital an Oblate Spheroid waveguide? I see the Hi-FI boys love these, and my priority is for best sound quality above all else.

Levyte357: Thanks for your interest, but my plan is to put the 1745s in some monitors when I have upgraded the mains.
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Points: 1587 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_B Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 11:30pm

You don’t necessarily need a horn that will operate down to 1K. If a horn is properly designed to work down to 2K it will be fine. The problem is proper mouth termination is not always a priority when horns are designed. As you realise with your design (how the size of the HF horn will impact on the mid horn) there is always a compromise.

For further reading click here.

Also look for papers by Keith Holland and Philip Newell:

Round the horn.
The sound of midrange horns for studio monitors.
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Moo View Drop Down
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Points: 21 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Moo Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2012 at 12:11am
I am aware of those articles, though I have to confess that I have scanned them and not read and understood them fully. 
I thought the towel around the end of the paper cone was interesting, and have actually tried it in my cab with acoustic foam linings on the outer halves of both the HF and Mid horns. I then carried out blind A/B testing of foamed and non-foamed cabs with both myself and other family and friends, and all preferred the Foamed versions. They sounded less harsh, more like music, and less like a horn. 
In an Ideal world I would construct my own elliptical oblate spheroid Horns, but I imagine the time involved would be Huge. It would be nice if manufacturers caught on to the Idea and started making them, but I have'nt found any yet except Gedlee's of course.


Edited by Moo - 24 February 2012 at 12:12am
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Tony Wilkes View Drop Down
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Originally posted by Moo Moo wrote:


Tony: I have read that it is critical to get a good match in the exit angle of the comp to the horn to avoid a cavity resonance in the join area. Is the Faital STH100 a good match for the exit angle on the BMS comps? Also is the Faital an Oblate Spheroid waveguide? I see the Hi-FI boys love these, and my priority is for best sound quality above all else.


If I ever recommend something it is done on the basis that I either own or have tried the item or that it comes highly recommended from pepes of whom I respect fully their opinion (and ears). Please bear in mind that with regards perceived sound quality opinions differ so wildly that personal recommendations should come with a "Government Health Warning"

In this case I use the STH100 in a few of my designs.  I cross using them >2k. For Hi-Fi use also ask steve_b who has got involved in this thread about his really nice fiberglass jobbies, they may be just what you are looking for. I am using them at the moment in a 12" +1 " job.

Tony
www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)
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I would second the comment about a lot of manufacturers being somewhat optimistic about the lower cut-off of their horns/waveguides.  For example, the ME10 which has been mentioned is spec'd down to 1.5kHz, IMO it doesn't get anywhere close.  I personally wouldn't use it lower than 2.5kHz but more likely 3.5kHz above an 8" driver etc.

One of the things to consider is that crossovers, especially passive ones are a long way from 'brick walls'.  Although you may be putting the crossover point at say 2kHz, to get a clean crossover between the mid and high sections, the compression driver/horn combination needs to be capable of supporting useful output until probably an octave below the crossover point.  Steeper crossover slopes can be used to mitigate this but have their own disadvantages.

The Celestion horn actually has quite a small mouth because of the large mounting flange.  For co-axial usage I would go for something with a much narrower surround, to get the largest mouth you can for the dimensions.  Personally I would also probably cut the mounting flange off and use a bracket off the driver mounting points to support the compression driver and horn inside the mid horn.

I would suggest the RCF H100.  If you trim it down, it's no bigger than the Celestion but will have a significantly lower cut-off.
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