# Which compression driver



## Veebee

Guys, interested to hear your thoughts on some compression drivers, 
I currently have a set of Veritas horns which have a 1.4" entry. I've got a couple of thoughts about what i can do with these. One is to make an adaptor that will turn them into a straight entry horn so I could mount either a 1 or 1.4" driver. Potentially mount some 2" midranges onto this adaptor aswell ala PB and his unity horn.

2nd option is to build a set of horns from scratch which will suit my car, this will give me the biggest mouth size possible to hopefully get these as low as possible, again this could potentially be a unity horn type set up.

I'm hoping to get the largest frequency range possible out of these, 300-20k would be nice, but might be a bit ambitious. I'd like the CD to get down around 1k, a little lower would be nice.

So onto the candadites- I haven't heard any of these just going off what i've read so any real world experiences would be great.

- Beyma- CP380M - Heard great things about the sound of these drivers, cheaper than the others though it's a 1" which would mean i would have to make at least an adaptor straight away

- Beyma cp385nd - the smaller size of this over the 38O is appealing but looks like the top end doesn't extend swell as the 380, again, 1" outlet has the same problems

- Beyma SMC65 - frequency range of 700-18k, which is more than the 1" 
drivers and looks a bit smoother than the next option but the top end of 18k concerns me

-Beyma SMC65Nd - frequency range of 600-20k interests me but very hard to find any subjective views of it. 

- your suggestions here.

Sorry for the long post, looking forward to hearing your opinions and experiences with these drivers and any others you can recommend

Cheers
Tim


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## instalher

i have won 2 canadian championships using the waveguides from usd audio.the bc3rt and the 7 series are really nice.check out there web page.


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## rawdawg

If I had a 1.4", I'd look into these interestingly shiny things.

1.4" Drivers


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## minbari

118dB? good god, you would only need 5 watts to run those, lol.


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## thehatedguy

I had a set of Beyma CP755/ND 1.4" drivers...probably some of the best around.

Other 1.4" drivers I would be checking out are the Radian 745NeoPB or the Faital HF144s.

TADs are the king dookie in pretty much any throat size though. You will pay for them and they are LARGE.


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## thehatedguy

I have built large horns...but the horns got WAY too big to fit in the car when you are trying to get below 500 hertz with any authority. I wouldn't be expecting too much below 450-500 hertz from the Veritas or any large car horn.

Rather than do Unity style horns, I would go with a midrange compression driver like the B&C DCM50 and add a supertweeter/tweeter for the high end information. this would give you more dispersion in the high frequencies and better "air" in the treble.

The BMS drivers are nice drivers...just that the coax drivers are, um, well, not well received in the home world.


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## thehatedguy

Actually the phenolic domed Selenium D405 if you can find them are supposed to be some of the better midrange compression drivers. However like most compression drivers that are meant to do midrange, they are a 2" exit driver. If you were stepping up to a 2" midrange only driver, the Community Light and Sound M200/M200A are some of the best you can find...barring spending a grip on JBL 2440 or even better the 2441s. The M200s are pretty tiny drivers whereas the JBLs are HUGE. The M200s only really go out to 4k or so due to their lack of phase plug.

You would want a pretty substantial tweeter though...not just any will do. You would ideally want your tweeter to be at least or more efficient than the compression drivers you are using.

The coax compression driver is a great solution on paper. The only one that really works well for high fidelity is the B&C DCX50. The BMS have problems with the phase plugs (this is universally agreed upon in the home HE world) and they just don't work that well for what we want to do with them.

This was something I was heavily involved in and researched from about 2004 to about 2010...when I sold my old Accord and had a family.


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## Eric Stevens

All the advice given is great but there is another option that has been left out.

There is a field coil version of the 2441 with a Brush Wellman Beryllium diaphragm. These are being made for some of the high end recording studios to replace the TAD 4001in the TAD monitors. They also replace the bi-radial TAD horn with a Bi-radial Tratrix design from Dr Bruce Edgar.

Now all I need is a large listening room again and a full field coil Edgar Horn system with some single ended goodness to drive them. 

Eric


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## thehatedguy

What you are talking about is what Mark Elridge did in his old 4 Runner. He had Altec 288s in there though...at one point. I think he did something else towards the end before he sold it.

And leave it to Eric to suggest some 20k dollar compression drivers...lol.

But what he says about a big room to enjoy it all is a hint...you really should be at least 1 wave length away from the horn's lowest frequency when using compression drivers for the sound to gel and the wave front to develop. And in a car it is really hard to get into the far field of anything except upper midrange and treble.


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## Eric Stevens

thehatedguy said:


> And leave it to Eric to suggest some 20k dollar compression drivers...lol.


What you mean we arent supposed to take out a second mortgage to fund our audio habit?


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## nubz69

From what I have seen, trying to get below 500hz you really start hitting diminishing returns. 

I have found that a balanced design will always out perform a system designed to maximize just one aspect.

If you want to get low take a look at the DE950TN or DE1050, they seem like interesting drivers.

You might want to consider getting creative with a wideband driver.


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## Ayanna

rawdawg said:


> If I had a 1.4", I'd look into these interestingly shiny things.


what u think about 118bd?


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## subwoofery

nubz69 said:


> From what I have seen, trying to get below 500hz you really start hitting diminishing returns.
> 
> I have found that a balanced design will always out perform a system designed to maximize just one aspect.
> 
> If you want to get low take a look at the DE950TN or DE1050, they seem like interesting drivers.
> 
> You might want to consider getting creative with a wideband driver.


The problem is not really the driver but the horn size. It gets really really too big and fast... 

Kelvin


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## Patrick Bateman

Veebee said:


> Guys, interested to hear your thoughts on some compression drivers,
> I currently have a set of Veritas horns which have a 1.4" entry. I've got a couple of thoughts about what i can do with these. One is to make an adaptor that will turn them into a straight entry horn so I could mount either a 1 or 1.4" driver. Potentially mount some 2" midranges onto this adaptor aswell ala PB and his unity horn.
> 
> 2nd option is to build a set of horns from scratch which will suit my car, this will give me the biggest mouth size possible to hopefully get these as low as possible, again this could potentially be a unity horn type set up.
> 
> I'm hoping to get the largest frequency range possible out of these, 300-20k would be nice, but might be a bit ambitious. I'd like the CD to get down around 1k, a little lower would be nice.
> 
> So onto the candadites- I haven't heard any of these just going off what i've read so any real world experiences would be great.
> 
> - Beyma- CP380M - Heard great things about the sound of these drivers, cheaper than the others though it's a 1" which would mean i would have to make at least an adaptor straight away
> 
> - Beyma cp385nd - the smaller size of this over the 38O is appealing but looks like the top end doesn't extend swell as the 380, again, 1" outlet has the same problems
> 
> - Beyma SMC65 - frequency range of 700-18k, which is more than the 1"
> drivers and looks a bit smoother than the next option but the top end of 18k concerns me
> 
> -Beyma SMC65Nd - frequency range of 600-20k interests me but very hard to find any subjective views of it.
> 
> - your suggestions here.
> 
> Sorry for the long post, looking forward to hearing your opinions and experiences with these drivers and any others you can recommend
> 
> Cheers
> Tim


The main reason that you'd use a 1.4" or a 2" compression driver is to get it to play low. But once you do that, you have to make the mouth bigger.

That conundrum is the main reason I have a pile of waveguides and horns in my garage, and I haven't touched the car in months. (well that, and this impending recession means I have to actually get my work done on time if I'd like to hold onto my job)

About the only way around this rule is to use the boundary of the car to extend the waveguide. Similar to what I did with the horns up on the dash, or similar to that car that has the Image Dynamics horns that are pushed so far back, they're practically flush with the firewall of the car. (I don't recall whose car it is - it's here somehwere)

If you try to make the mouth to small, you get craploads of group delay and it's basically unlistenable. There are only two solutions:

1. make the mouth bigger
2. raise the crossover point (which defeats the whole purpose of a 2" throat)

That's it! If you want to have some fun with this, download a copy of hornresp and play around with the LeCleach curve. The group delay on that curve is to die for. (LeCleach horns have some other problems though. As with everything in audio, there is no free lunch)


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## radwilsons5803

instalher said:


> i have won 2 canadian championships using the waveguides from usd audio.the bc3rt and the 7 series are really nice.check out there web page.


X2. had a set of usd audio's ten years ago and they were amazing to say the least. Im sure the others are just as impressive


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