Beyma TPL-150 Just Might be Worth the Price!

[Loren42]

I was ready to cancel the project, but my girlfriend kept edging me on, so I just completed a simple 2-way with the Acoustic Elegance TD-15H and a Beyma TPL-150 crossed at 1.2 kHz.

I still need to dial in the crossover, but my initial impressions of the Beyma are very positive.

Clarity is much improved over the Morel tweeters and Audax mid I had been using in a different speaker.

They also have a perceived wider horizontal sweet spot over the dome tweeters.

I will be doing formal measurements soon to understand what I really have, but I think I am getting my money's worth out of these Beymas. It is an expensive experiment.

[CharlieLaub]

Ah, I saw that driver recently and was interested until I got turned off by the price: US$400 each! That is a little much for a tweeter, my friend, even if you cross over at 1.2k Hz. There are direct radiator (dome) tweeters that can be crossed down there unless you are listening at high SPLs that cost much, must less.

Now that you bought them, I hope that you find them worth the price!

Maybe I am just jealous!!!

-Charlie

P.S. Are you really using a 15" driver to make a 2-way speaker???
That's really asking for poor off axis performance around 750Hz and up, I think, but depending on how the system and crossover are designed it could work, maybe. AE Speakers doesn't have the FR posted on or off axis for this driver. Did you happen to measure it or see it posted somewhere by any chance?

[Loren42]

Originally Posted by CharlieLaub

Ah, I saw that driver recently and was interested until I got turned off by the price: US$400 each! That is a little much for a tweeter, my friend, even if you cross over at 1.2k Hz. There are direct radiator (dome) tweeters that can be crossed down there unless you are listening at high SPLs that cost much, must less.

Now that you bought them, I hope that you find them worth the price!

Maybe I am just jealous!!!

-Charlie

P.S. Are you really using a 15" driver to make a 2-way speaker???
That's really asking for poor off axis performance around 750Hz and up, I think, but depending on how the system and crossover are designed it could work, maybe. AE Speakers doesn't have the FR posted on or off axis for this driver. Did you happen to measure it or see it posted somewhere by any chance?

Yup. I used these drivers in a different design with a lower crossover point, so I don't have the off-axis data for this design - yet.

Initial impressions seem to be favorable, but I would not bet anything until quantitative measurements are done, then I will post those results.

I have been itching to try a 2-way, but turned off with the idea of a horn due to its complexity. The Beymas rekindled that desire.

So far I have a number of independent ears that feel it is better than the 3-ways I had. That is my listening impression as well. It is a good start.

[Loren42]

Here are a little more details. I really did not have a lot of time to play with this, so sorry for the lack of details.

First, the impedance plot using the highly controversial Woofer Tester 2:



The next plot is a simple 1 meter sweep. Note, my room limits the resolution to about 650 Hz! This is not very detailed, but it does give us a glimpse of the marriage of the two drivers.

I did an ad-hoc off axis plot, but it was overwritten, so I have nothing to show. Basically, it looked like the TD15H directivity drops off at just about 1 kHz when you are 60° or greater off-axis. Since the crossover point is 1.2 kHz there is a slight hole of about -6 dB, if memory serves (according to my ad-hoc plot).

I need to get the cabinet outside before I commit to any findings so that Holm can do a better sweep without all the internal reverberation in the room.



The on-axis sweep for the Beyma pretty well matches the factory frequency curve, so I have some confidence in the data. I think I need to boost the Beyma's output a few dB.

The Beyma is attenuated 7 dB (according to the crossover calculations for my two resistor L-Pad). I am thinking that 2 to 3 dB boost would be better.

[454Casull]

Originally Posted by CharlieLaub

P.S. Are you really using a 15" driver to make a 2-way speaker???
That's really asking for poor off axis performance around 750Hz and up, I think, but depending on how the system and crossover are designed it could work, maybe. AE Speakers doesn't have the FR posted on or off axis for this driver. Did you happen to measure it or see it posted somewhere by any chance?

Unless the diaphragm behaves non-pistonically, off-axis response is generally dictated by the diaphragm's size.

[CharlieLaub]

Originally Posted by 454Casull

Unless the diaphragm behaves non-pistonically, off-axis response is generally dictated by the diaphragm's size.

Even if the driver is operating "pistonically" the different path lengths from various parts of the cone will begin to cause interference and this will cause the SPL to fall as you move off-axis.

I was rather surprised that the poster was using a 15", as I thought that this would be really be usable only up to 500Hz or so, but I am not familiar enough with modern drivers of this size intended for "full range PA" use to know exactly how high you can push the crossover point before getting a hole in the response off-axis. Also I thought that maybe this was intended in the design for some reasons... maybe Loren42 can comment on that - on the design goals?

-Charlie

[Loren42]

Originally Posted by CharlieLaub

Even if the driver is operating "pistonically" the different path lengths from various parts of the cone will begin to cause interference and this will cause the SPL to fall as you move off-axis.

I was rather surprised that the poster was using a 15", as I thought that this would be really be usable only up to 500Hz or so, but I am not familiar enough with modern drivers of this size intended for "full range PA" use to know exactly how high you can push the crossover point before getting a hole in the response off-axis. Also I thought that maybe this was intended in the design for some reasons... maybe Loren42 can comment on that - on the design goals?

-Charlie

The goal was to use the TD15H, which I already had, and attempt to mate it with a suitable driver for a two-way design.

I can't find my original plots, but the TD15H does a little better job off-axis than the typical 15. That was done on a different cabinet.

We have bad weather here this week, but when weather permits I can get this outside to do a off-axis plot of the woofer, then the tweeter, to see what I really have.

[454Casull]

Originally Posted by CharlieLaub

Even if the driver is operating "pistonically" the different path lengths from various parts of the cone will begin to cause interference and this will cause the SPL to fall as you move off-axis.
-Charlie

I did not say that a 15" driver is a point source (I am well familiar with drivers having less off-axis response as frequency increases). I merely pointed out that directivity is typically inversely proportional to diaphragm size.