# Any advice for these USD Audio D2 RTMT horns and drivers?



## Inigma (Mar 17, 2012)

Hi. I bought a set of used never mounted USD Audio D2 RTMT horn/waveguides off of here a little while back. I'm going to mount them in my Thunderbird Super Coupe. Any Other advice other than dampening the horn bodies and mounting them as far back and wide as possible?

I plan to cross them at 1.25k-1k, depending on which amp I put in the car. Are the D2 or D200 drivers good down to 1k? Any lower? Are these drivers pretty decent still? Is there any other budget friendly, entry level, driver that would be noticeably better at around $100 each that I should get for these waveguides before installing them?


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## Patrick Bateman (Sep 11, 2006)

If you're using piezo tweeters, these will sound better:

Celestion CDX1-1445 Ferrite 1" Compression Driver 20W

To my ears, the Eric Stevens HLCDs and the JBL waveguides sound better than the USD horns

Note that you won't be able to use the piezo crossover with the Celestion compression driver


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## porscheman (Jan 1, 2012)

the d2s arent piezos, the d1s were


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## Inigma (Mar 17, 2012)

The link below shows what I have, but I only have the waveguides, drivers, and grills. I do not have the mids or the crossovers. 

USD seems to recommend an 800hz crossover.

USD Audio WaveGuide D-200

I'll post some pics laterif any one is interested.


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## thehatedguy (May 4, 2007)

I would be willing to say looking at the sensitivity numbers and the fact that USD states it has it's own crossover and protection circuit built in screams piezo drivers. Only a piezo driver would not need it's own crossover element.


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## rockin (Sep 13, 2012)

Inigma said:


> Hi. I bought a set of used never mounted USD Audio D2 RTMT horn/waveguides off of here a little while back. I'm going to mount them in my Thunderbird Super Coupe. Any Other advice other than dampening the horn bodies and mounting them as far back and wide as possible?
> 
> I plan to cross them at 1.25k-1k, depending on which amp I put in the car. Are the D2 or D200 drivers good down to 1k? Any lower? Are these drivers pretty decent still? Is there any other budget friendly, entry level, driver that would be noticeably better at around $100 each that I should get for these waveguides before installing them?


I run these now in my '88 Monte because I absolutely can not fit a larger (Radian) driver. Get on an RTA after you've them installed. Mine play down to 900 hz - but I suspect how low they go will depend on your car and install. I also run super tweeters with these crossed over at 14K hz.


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## Eric Stevens (Dec 29, 2007)

The pictured D200 driver is a piezo element compression driver. Great for abusive listener but not the best for SQ, but can be tweaked to sound good.


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## Inigma (Mar 17, 2012)

Thanks everyone for the reply's. I asked the question right around when my second child was born so I've been busy. 

I have the ES ultras on full bodies in my non-daily driver. I love them..

I was planning on getting these USD audio's into my daily driver over these holidays, but alas I've spent all my time with the family and haven't been out in the garage much. It didn't help either that I got a cold the Saturday before Christmas, then passed it to the wife, the kids.

I have an extra set of barely trimmed full bodies I bought off here a little while back to switch to if needed, but I was saving them for a later project. 

Anticipating wanting better drivers for the USD's though, I got a good deal on (1) JBL 2408h-1 to listen to and am strongly considering ordering a pair of the celestion's as Patrick had suggested. Oddly the 2408h-1 has a made in China sticker on it which I find odd as I thought they were made in Mexico. When I get a second one, I'll have to compare the two. 

This question probablly belongs as a seperate thread, but why was the selenium d2500ti discontinued? What was its replacement? 

I've also got plans to build some econowaves for the house out of some of the Pyle JBL knock off waveguides (unless I find a good deal on the JBL waveguides) and probably some 12" woofers. I just gotta find some grills that keep little fingers off of woofers (and time to build cabinets). 

Anyways, I just wanted to say thanks again.


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## Patrick Bateman (Sep 11, 2006)

The Celestion and JBL perform pretty darn similar. I wouldn't bother buying the Celestion if you have the JBL. The JBL used to sell for about $60, but now it sells for $166  A similar thing happened to the Celestion; it once sold for $35 now it's around $100.

IIRC, the JBL is a little bit more efficient than the Celestion. It's noticeably larger. Mine are made in Mexico.

As for the Selenium, I can only speculate. Perhaps it's due to their acquisition by JBL. JBL has definitely been moving towards neodymium across their product line. Even a lot of their "cheap" speakers use neodymium.


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## thehatedguy (May 4, 2007)

The pisser about the JBL is that you can get a "real" BMS 4540 new cheaper than you can get the used JBL cheaped copy.

The 2408h is different than the 2408n-1. Usually when there are suffixes with JBL it means they did something to cheapen the costs...like a different phase plug and moving production offshore.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> The pisser about the JBL is that you can get a "real" BMS 4540 new cheaper than you can get the used JBL cheaped copy.
> 
> The 2408h is different than the 2408n-1. Usually when there are suffixes with JBL it means they did something to cheapen the costs...like a different phase plug and moving production offshore.


The phase plug on the JBL have changed quite a bit. The dude that designed the phase plug came over to JBL from Cerwin Vega a few years back. He has a patent on the phase plug and AFAIK BMS is not using it. The BMS design is patented, and JBL is likely licensing it from BMS. So the 2408H-2 combines innovations from both BMS and JBL.
I'm too lazy to dig up my measurements, but I measured both the 4540ND and the 2408H-2 on the same waveguide, and IIRC the JBL had more output.

The 2408H-2 is significantly larger, about 25%.

It's a nice driver, I'd use it more if it wasn't so expensive. Heck, it might just be the best compression driver I own.

Having said all that, sonically the differences are pretty subtle. It's not like we *need* the extra output! 









As an aside, I recently went from the Vifa ring radiator on a waveguide, to the Celestion CDX1-1425. When I went from Celestion to Vifa, I thought the Vifa sounded a bit odd, almost like it was rolled off.

But now that I'm back to using the Celestion, I gotta admit, the Celestion sounds "brittle" in comparison to the Vifa. IE, once you acclimate to the Vifa ring radiator, a compression driver sounds a bit too bright. The excellent sound of the Vifa may well be due to lack of higher order modes; the interface between the ring and the waveguide is about as good as it gets.

I also had a chance to compare the Danley SH50s with the BMS 4550 ($150) to the Lambda Unity Horns with the TAD 2001 driver. ($1000) To my ears, the TAD was a little bit cleaner at the top. For a very small fraction of the price, the Vifa is awfully close.

TLDR: the $20 Vifa ring radiator makes a lovely driver for waveguides. Maybe one of the best.


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## mikey7182 (Jan 16, 2008)

Sorry to dredge this up... Patrick, you're saying that the 2408H-2 is 25% larger than the BMS 4540? The info I found online says the JBL is 2.5" OD, while the BMS is 2.8" OD. Is the JBL just deeper? Or are you saying the 2408H-2 is bigger than the original 2408H? I'm in need of some SMALL thread-type compression drivers, and remembered the 2408, 2408-1 and 2408-2 as well as the BMS and ended up back here. I currently have a pair of Selenium D2500 and at 3.2" OD, they are too large. I need to sell/part with them I suppose, and find something smaller.


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## Patrick Bateman (Sep 11, 2006)

mikey7182 said:


> Sorry to dredge this up... Patrick, you're saying that the 2408H-2 is 25% larger than the BMS 4540? The info I found online says the JBL is 2.5" OD, while the BMS is 2.8" OD. Is the JBL just deeper? Or are you saying the 2408H-2 is bigger than the original 2408H? I'm in need of some SMALL thread-type compression drivers, and remembered the 2408, 2408-1 and 2408-2 as well as the BMS and ended up back here. I currently have a pair of Selenium D2500 and at 3.2" OD, they are too large. I need to sell/part with them I suppose, and find something smaller.


Yep. The 2408H-2 is noticeably heavier and beefier than the 4540ND.

The 2408H-2 has a number of improvents to the phase plug that are notable, and I believe that leads to a depth which might be a little bit less.

The Celestion CDX1-1425, 4540ND, and 2408H-2 are all very small though.

If you really wanted to go small, I'd check out the neodymium ring radiators. A ring radiator produces a flat wavefront, and you can basically just bolt them onto a waveguide.

You'll need a dremel or a hack saw to shorten the depth of the waveguide though.

Check out my pics of the Pyle waveguide with the Vifa ring radiator, it's REALLY small. Sounds good too.

On the downside, the power handling and maximum SPL is easily 10dB less than a compression driver, maybe more. Those neo tweeters don't have much of a voice coil and can't handle the abuse like a CD


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## mikey7182 (Jan 16, 2008)

The 2408H-2 looks promising. Jack's Music Factory says they're 2.5" OD and weigh 1 lb, and that they're an upgraded replacement for the original 2408H. I just wish neo wasn't so GD expensive.  It has gotten ridiculous lately.


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## Jesus Christ (Aug 3, 2010)

Here's a d2500 and 4540 for size comparison.


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## Patrick Bateman (Sep 11, 2006)

mikey7182 said:


> The 2408H-2 looks promising. Jack's Music Factory says they're 2.5" OD and weigh 1 lb, and that they're an upgraded replacement for the original 2408H. I just wish neo wasn't so GD expensive.  It has gotten ridiculous lately.


I had high hopes for it, and I *do* thing it's a better driver. But all of the small compression drivers sound pretty similar; I can't tell a 4540 apart from a 2408H-2.

Main advantage of a 2408H-2 is more output.

But we're not exactly "limited" on output already, y'know?

I built some waveguides inspired by the waveguide from the JBL M2, and *that* really was quite a revelation; it really and truly *does* widen the bandwidth.

I posted some measurements over at diyaudio, but the whole thing went over like a lead baloon lol
(I don't think anyone noticed, or my posts made no sense.)

Basically the M2 waveguide lets you create a waveguide shape that blends the virtues of a waveguide with the virtues of a horn. You get constant directivity, but you also get flatter response and wider bandwidth than a conical waveguide will get you.

They're a p.i.t.a to manufacture and they're patented, which is probably why I'm the only person I've seen clone them.


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## Patrick Bateman (Sep 11, 2006)

Here's an elaboration of what I said in my last post, about the M2 waveguide.









In the center of this pic is a waveguide, and a good one. It's the QSC that sells for $35 at Parts Express. The advantage of a waveguide is that the response shape doesn't change as you move about the coverage area. For instance, if you're in front of the waveguide, or 45 degrees off axis, the response shape is basically the same. This is due to the flat walls; it basically "spreads" the sound out over the coverage angle.
The disadvantage of a waveguide is that it rolls off at high frequency. So you have to EQ, and a LOT of it, to get flat response. You may need to use as much as ten or even twenty dB of EQ to get it flat to 20khz.









This is a horn. The advantage of a horn is that it has flatter response than a waveguide, and potentially better impulse response. The disadvantage of a horn is 'horn honk', and it's directivity narrows as frequencies get higher.









The M2 is a interesting curve. On the horizontal and the vertical axis, it's shaped like the constant directivity horns from the 80s. But on the diagonal axis, it's shaped like a JBL PT waveguide.

From my measurements, it seems to offer the advantages of both designs. You get the constant directivity of the QSC, but more output and wider bandwidth like a horn.

Neat.

The QSC is still smoother though, lol. The QSC is really, really good.


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## mikey7182 (Jan 16, 2008)

Interesting stuff. Thanks Patrick!

And thanks for the pics, Jesus!  That was very helpful as well.


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