AMTPRO-4 "open back" tweeters - PE deal today

JohnR · « **on:** 10 May 2014, 01:23 pm »

https://www.parts-express.com/dayton-audio-amtpro-4-air-motion-transformer-tweeter-4-ohm--275-094

From the product description, "Open back design permits dipole or chamber loading"

Couldn't find any reports (on a quick search) of using it in dipole/open back mode. I'd also guess vertical dispersion will be a bit limited at high frequencies du to its length. Still...

Brad · « **Reply #1 on:** 10 May 2014, 02:33 pm »

You didn't look very hard then John

That's a good price.

I still want to hear the new AMT700 and Beyma TP150H in comparison, but I'm quite happy with mine in OB.

JohnR · « **Reply #2 on:** 10 May 2014, 03:40 pm »

Oops

sorry Brad. Got any pics? What frequency/slope are you crossed over?

Brad · « **Reply #3 on:** 10 May 2014, 03:52 pm »

I have pics from LSAF that I'll get posted today.

Currently using a passive 12db cross at 1900hz.
In the process of building a Boozhound active xover kit, and will try 1600hz and 1200hz, also at 12db.
The integration was already quite good with the passive.
That AMT can handle quite a bit of power too.
I have the AMT and the 15" mid mounted in parallel horizontally, centered on 41" off the floor.
Baffles are a bit large at 24" w x 52" h.

$99 is a pretty good deal - I think PE had them for $148 when I purchased.

JohnR · « **Reply #4 on:** 13 May 2014, 08:07 am »

How are those pics going Brad?

I'll get my pair next week. Reboot of my ob project - neo10 instaed of cone mid and these instead of neo3. Just lucky I clicked on that link that day!

Brad · « **Reply #5 on:** 13 May 2014, 02:26 pm »

They're still on the camera!
Hoping to get them posted tonight.

(thanks for the reminder - I have quite a few pics to process)

jimbones · « **Reply #6 on:** 13 May 2014, 02:44 pm »

General question but related to this driver: I am fairly new to diy speaker building but i notice that the frequency response of this driver appears ragged, yet I read reviews that say it is very good. So the question is this, if a driver were to have uneven frequency response would that rule it out as a driver for hi end speaker application or can you tell from the manufacturers data? Does it have to be "ruler flat" to begin with?

Brad · « **Reply #7 on:** 13 May 2014, 11:11 pm »

My web host moved the server I was on, and I've got to get Piwigo working again.
Uploaded the images here for now.

For scale, the baffles are 52" high.

JohnR · « **Reply #8 on:** 14 May 2014, 01:29 am »

Whoa!! I like

Quote from: jimbones on 13 May 2014, 02:44 pm

Does it have to be "ruler flat" to begin with?

No I don't think so... Only the final result matters - ?

Brad · « **Reply #9 on:** 14 May 2014, 01:46 am »

I did notice the published response curve, AFTER I had already purchased them

I was a little concerned about it, but they sound pretty smooth to me.
I am going to get some measurement equipment so I can keep an eye on the results with my active crossover kit, as I tweak things.

jimbones · « **Reply #10 on:** 14 May 2014, 08:08 pm »

Quote from: JohnR on 14 May 2014, 01:29 am

Whoa!! I like

No I don't think so... Only the final result matters - ?

Thanks because I'm worried if it is ragged to begin with what will it look like after I get ahold of it

mightym · « **Reply #11 on:** 14 May 2014, 10:56 pm »

I heard the speaks Brad pictured at the Lone Star Audio Fest a couple of weekends ago. I really liked them.

I was disappointed to find that they didn't stay on sale long enough for me to find this thread, and go looking for that bargain. Day late and a Dollar short, as usual.

John

JohnR · « **Reply #12 on:** 15 May 2014, 02:56 am »

Yeah $100 ea was a real bargain I think. Sorry

Well, I hope it was a bargain hah hah.

Quote from: jimbones on 14 May 2014, 08:08 pm

Thanks because I'm worried if it is ragged to begin with what will it look like after I get ahold of it

It doesn't look too bad to me. The datasheet doesn't say what the measurement conditions were. I'll be using active DSP anyway so the frequency response shown on the datasheet is not that much of a concern, maybe there are other issues, don't know yet. Mine actually arrived today already, they're quite deep internally which will probably cause some issues in "dipole" mode. Anyway, I'll see how it goes.

Brad · « **Reply #13 on:** 15 May 2014, 01:36 pm »

They are quite heavy too, for a "tweeter"

One comment I remember from LSAF from someone new to OB: "These sound almost as good from behind"

jimbones · « **Reply #14 on:** 15 May 2014, 02:18 pm »

Quote from: JohnR on 15 May 2014, 02:56 am

Yeah $100 ea was a real bargain I think. Sorry Well, I hope it was a bargain hah hah.

It doesn't look too bad to me. The datasheet doesn't say what the measurement conditions were. I'll be using active DSP anyway so the frequency response shown on the datasheet is not that much of a concern, maybe there are other issues, don't know yet. Mine actually arrived today already, they're quite deep internally which will probably cause some issues in "dipole" mode. Anyway, I'll see how it goes.

looking at the graph between 2k and 13k it looks like overall a 13 db spread. theres a dip at 2k and a peak at 12-13k. after the peak there is quite a slope down. (Not that I can hear much in that region

)

Brad · « **Reply #15 on:** 15 May 2014, 03:18 pm »

Quote from: jimbones on 15 May 2014, 02:18 pm

looking at the graph between 2k and 13k it looks like overall a 13 db spread. theres a dip at 2k and a peak at 12-13k. after the peak there is quite a slope down. (Not that I can hear much in that region )

Ditto on the HF hearing ability

. I hadn't even budgeted for a tweeter to begin with, then I thought someone else might listen to the speakers at some point

JohnR · « **Reply #16 on:** 16 May 2014, 12:36 am »

The rising response and falling top end can be eq'ed easily, the issue is more what the dispersion pattern is. For my purposes a smaller model would have been better but the Dayton ones are not open back and something like the Mundorf amt23 is $400 each..! From Brad's impressions I'm fairly confident the driver will be good to work with.

matevana · « **Reply #17 on:** 24 May 2014, 04:06 pm »

I'm testing 2 different pairs of the AMTPRO-4 for my Hestia V design. They do some things very well and some other things that I am still working through. Interesting that they recently changed the face plate on these slightly, to address a vertical dispersion issue.

JohnR · « **Reply #18 on:** 25 May 2014, 12:41 pm »

I did some quick measurements today, didn't see anything too much to worry about other than what you'd expect from its size. What are the things you noticed?

matevana · « **Reply #19 on:** 25 May 2014, 01:26 pm »

The dip in the Dayton plots around 2k might not be problematic if crossed in that region, but I'm using them in a 3 way @ 7k so it may be something to contend with. My samples have not measured the same but I am miking them in-room with the felt pads removed for dipole use. I'm guessing the Dayton plots were measured with the felt still in place. Most of my measurements including sensitivity were different with the felt pads removed.

Also I'm getting an annoying sibilant "T" on one of the pairs but not the other... this may be a function of the old vs new face plate design. I'm waiting for a better quality cap to see if that improves things here as well.

That being said the overall presentation is still very nice and the AMT air motion technology is faster than most domes. It compliments dipole bass nicely. I plan to use them in my next design and just work around a few minor things.