Dayton Audio D250P-8 & 811B : impedance vs. Hz plots

RE: Dayton Audio D250P-8 & 811B : impedance vs. Hz plots, posted on July 19, 2014 at 21:54:07
freddyi Audiophile Posts: 3852 Joined: December 6, 2001	with that flat on an input impedance there would be less interaction between the network and driver - it could be run even electrical 1st order if xovered high enough and the amp happy with the load. Karlson Evangelist

RE: Dayton Audio D250P-8 & 811B : impedance vs. Hz plots, posted on July 20, 2014 at 04:23:40

deathtube 667

Thanks for that info.

I looked a bit on the Altec Heritage site and didn't see a Zobel network for the HF horn.

I was not sure if I should use one or not, but the Dayton driver has a weird impedance graph compared to most I have studied.

The horn is crossing over first order at 1.8KHz.

I was looking at some compensation networks because the high Hz's start to roll off at about 10KHz as measured at my listening position.

Tom Brennan posted one that has a cap and resistor in parallel across the top of one of 2 series fixed resistors from + to - on the horn.

RE: altec compensation circuit..., posted on July 20, 2014 at 10:04:30

deathtube 667

The Altec compensation circuit helps.

Both measured and from a subjective listening aspect.

I won't get much better bass from the 12" woofer and the high end is at the limits of what I can hear.

Edit: found another circuit, just a .47uF cap and 25 ohm resistor in parallel to pad the midrange output down 12dB.

Not sure how a Zobel will affect the compensation circuit.

Still trying to figure it out.

The highs sound OK, but maybe should have less measured roll off.

RE: altec compensation circuit..., posted on July 21, 2014 at 13:36:07
freddyi Audiophile Posts: 3852 Joined: December 6, 2001	that's a real nice graph overall - 811 have a bit less hot top than 511 Karlson Evangelist

RE: compensation circuit...another try, posted on July 21, 2014 at 14:19:04

deathtube 667

hello,

I removed that Altec comp circuit and tried a simple RC parallel network on the output of the crossover cap.

Before work, I tried .47uF//25 ohms and the Zobel, no L-Pad.

It sounded smooth, but when I got home and measured, the high end was rolled off too much.

I played around with various combination of resistors and caps in the comp RC network while sweeping pink noise in ARTA.

Ended up with a 5uF//25 ohms and the Zobel before calling it quits.

The integration between woofer and horn sounds a bit better.

The high end rolls off a bit more this way, but there is enough high Hz to hear cymbols or high hat on drums well enough.

My next step will probably be an active 2nd order crossover with opamps and a comp circuit for the horn.

Not sure where I will end up with this since I have a non-Altec compression driver and woofer.

Edit: crossed over the 811B at 1KHz 1st order with Zobel and 1.5uF//15 ohm compensation filter.

The lower crossover point seems to be needed to use something close to .47uF//25 ohm compensation recommended on another site.

Ran the woofer full range with just a Zobel, no crossover for a while.

Still a work in progress.

RE: Dayton Audio D250P-8 & 811B : impedance vs. Hz plots, posted on July 23, 2014 at 04:22:30

Don M
Audiophile

Posts: 193
Joined: July 17, 2000

There are a series of DIY builds by Zilch posted that include in some cases the B&C DE250, which some people believe was used for the design of the D250-P.

You will find details of the crossover designs including measurements at the following link.

DonM

Econowave DIY Projects

RE: great ..., posted on July 23, 2014 at 06:35:45

deathtube 667

Thank you.

I'll check it out.

My mistake was not overlaying the woofer and horn on the same graph so I could see where they were crossing over acoustically in room.

My crossover points were not correct, there was too much overlap between drivers and the 55-1220 woofer does not sound best running full range.

I try again with a higher order much lower Hz crossover on the woofer.

Maybe I will be able to blend in the horn first order if I do that.

High Efficiency Speaker Asylum

Dayton Audio D250P-8 & 811B : impedance vs. Hz plots

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