strange measurements from Peerless 830883 mid

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jimbones

Member
2004-11-08 5:18 pm
ny
Hey all,

Dumptruck and I have been wrestling with doing a OB design and I can't for the life of me understand why I am getting this weird saddle shaped response on my OB mid. There is a 10db dip at 1k. But the response is down by a wide freq range in the middle see graph. The baffle is 11 1/2 w and wings are 4 inches deep on the side. Do you think this is due to the OB? If you look at the spec sheet the response is nothing like that, unless it is my room.


saddle response.jpg
 

deicide67

Member
2008-08-20 9:42 pm
Hi Jim,

I'm not sure about everything, but I do agree that it is "similar" to published data. Maybe not as extreme. I remember seeing the measured response of my drivers on the baffle, and they had the same smile:)

4DDF98F9-0FF8-4D5D-9D8D-C65B1566432B-12368-00000BB283ED972E.jpg


After the crossover, this is the simulated response. We have not measured them since the completion, but I'd bet they are very close to the simulated response.
 

jimbones

Member
2004-11-08 5:18 pm
ny
One of the things we are struggling with is that when using PCD to design it appears that the mid is significantly lower sensitivity than the Dayton RS270. But the specs look to be within 1 db of each other. When I listen to them they don't sound like they are measuring. SO we are going crazy with the mid response.
 
I don't know of sensitivities, but the response of the Peerless HDS is "real" to me. The lower peak is dipole peak and higher peak is driver's rising response at 0¤ http://www.audio-components.co.uk/pdf/products/830883.pdf

I don't understand much of mathematics and passive xo design, but I do know that a minidsp is a wonderful thing! The problem is that you'll need a bundle fo amplifier channels!
 

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jimbones

Member
2004-11-08 5:18 pm
ny
Matches

I don't know of sensitivities, but the response of the Peerless HDS is "real" to me. The lower peak is dipole peak and higher peak is driver's rising response at 0¤ http://www.audio-components.co.uk/pdf/products/830883.pdf

I don't understand much of mathematics and passive xo design, but I do know that a minidsp is a wonderful thing! The problem is that you'll need a bundle fo amplifier channels!

Ok i see the upper end response matches fairly well. I also assumed the lower peak was a dipole peak. I xo at 300 and 2500 so maybe I adjust the points just enough to mask it :D
 

jimbones

Member
2004-11-08 5:18 pm
ny
Are you saying the miss are more pronounced or laid back? Is the RS-270
open also?

I would think the rs-270 would be lower efficiency open.

Where are you crossing? I'm crossed at 300Hz to mine. 3rd order if I recall.

The RS270 is in a sealed box. Sorry i wasn't clear on that. The mid sounds (to my ears) about the same efficiency as the RS270, but when I plot the Fr it appears lower (other than the peaks.) I think I am going to have to design th XO and remeasure and see if the mid still looks low.
 

jimbones

Member
2004-11-08 5:18 pm
ny
I'm not sure. Mine have two AE IB15s and I had to pad the 830883 as well as the BG neo3s.

You will need to roll them off fairly steep to bury the upper range breakup
And the dipole peak. Your RS270 should play up into the 300s with ease.

Blair

Oh nowI see, I wasn't able to put Decide67 and Blair together, hey Blair, thanks for your support.
Where did your dipole peak occur? The peak is affected by baffle dimension etc so i was thinking if i have to play with the baffle or side wings.....

Jim
 

deicide67

Member
2008-08-20 9:42 pm
If I remember the original files correctly, the peak on my baffles was between 250-300Hz. My baffles are ~19" wide with the driver at around 3-4" offset.

I have tried several times to change my screen name here to no avail. It's somewhat offensive in nature, and from 10-15 years ago when I was into heavy metal:)
 
If it can be helpful in any way here is the frequency response I've measured from my peerless 830883 (on a 20 cm wide baffle) - It is from the Nomex 164 by Troels Gravesen so its in a ported 2.5-way setup :)

EDIT: The measurement is taken from 1m and the response window is 10 ms - hopefully eliminating most reflections.
 

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jimbones

Member
2004-11-08 5:18 pm
ny
Thanks all very much

If it can be helpful in any way here is the frequency response I've measured from my peerless 830883 (on a 20 cm wide baffle) - It is from the Nomex 164 by Troels Gravesen so its in a ported 2.5-way setup :)

EDIT: The measurement is taken from 1m and the response window is 10 ms - hopefully eliminating most reflections.

Well, I notice the rising response on the upper end which tracks the spec, but the lower end is flat where mine has the dipole peak.

So that clarifies the "saddle shape" of my measurements. I will need to play around with the XO to minimize the effects. Thanks to all for your help i think I understand the measurement profile.
 
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