Damaged 511b

[gil393]

Just a quick followup. I worked it out with the seller, 25% off the purchase price. Not great but OK.

I finally got them hooked up and boy was I disappointed. They sounded like a transistor radio in a coffee can. Turns out all of that stuff below 500hz makes a difference. I pulled out an old pair of Advents and put those on the bottom end, played with the eq, and balance between top and bottom and they sound pretty nice. Really, loud in an all concrete basement if need be.

The problem is, zero, none, nada, top end. I'm doing a/b/c comparison between the straight Advents, some Magenepan MMGs, and the home brew. Even with the eq pushed to the max +12db from 8K+ I can't get any real top end, especially cymbals and bells. I hear them, muted pretty much, but the "sizzle" for lack of better word is missing.

I pulled the covers and these have original screw top 21545 diaphragms. They look to be in good condition. The wires from the cover to the diaphragm have crimp connectors with spades on both end. Other than that they look good. I guess I need new diaphragms to get some top end. The GPA pascalites seem to be the preferred solution. My question is, will these make a difference and what will the power handling be. I'm aiming for a 120db system to allow close to reference levels at 45 feet for home theater usage. I think the Symbioteks are already getting me close enough but I'm not sure about other diaphragms.

One final question to help out a newbie. How to I tell how much power I'm putting into them? I'm using an Ashly FET-200 (100watts at 8ohm) which has indicator lights in 3db increments down to -27db. At normal listening I can't even get the -27db light to come on. Turned up higher I can get the -18db light flicker occasionally. My, likely faulty, understanding is that power doubles every 3db so -3db is 50watts, -6db is 25 watts, etc. Was I really only putting in 1.5 watts at -18db?

Sorry to have so many questions. I want to make sure I don't blow up what I have and see if I can get it to sound a little better.

Thanks!

[bowtie427ss]

Was I really only putting in 1.5 watts at -18db?

Probably, allow a ~10% window of error. Exact power input is a difficult thing to calculate as it's impedance dependent, and the impedance is frequency dependent. 8/16 ohms is a nominal or average rating on a driver. The acoustic load(horn) and frequency will determine actual impedance seen by your amplifier.

I'm aiming for a 120db system to allow close to reference levels at 45 feet for home theater usage.

Pascalites and an XO of 800hz or higher, 1200 would be preferred, at least 2nd order.

I hear them, muted pretty much, but the "sizzle" for lack of better word is missing.

Pascalites.

I'm using an Ashly FET-200

Likes me some Ashly's, got a short stack of em here.

[RonSSS]

You didn't mention which drivers.

[bowtie427ss]

You didn't mention which drivers.

21545 is the stock 8 ohm diaphragm used in 807-8A's and 808-8A's most commonly found in 70's PA/MI/stage speakers. It's a safe bet they're 807's or 808's, hopefully 808's if the OP wants to wring 120db out of them.

[gil393]

You didn't mention which drivers.

Sorry, 808-a. They seem to be in good condition but I don't know their history. I'm going to go with the Pascalites. The only two questions are, with or without the backing cap, and should I send them in to GPA for recharge? I'm leaning towards keeping the backing cap, using an 800ish crossover (3rd order) and sending them in. Will I get top end close to a tweeter, keeping in mind I can only hear to 14k?

[bowtie427ss]

Will I get top end close to a tweeter, keeping in mind I can only hear to 14k?

How "close" will depend. Consider that the Altec systems using this horn/driver combination that offered "extended" HF use networks that were contoured/equalized. Some equalization to bring down the mids can go a long way toward smoothing the response to effectively extend overall response.

[gil393]

How "close" will depend. Consider that the Altec systems using this horn/driver combination that offered "extended" HF use networks that were contoured/equalized. Some equalization to bring down the mids can go a long way toward smoothing the response to effectively extend overall response.

After I plugged in an equalizer, dropped the mids and boosted the highs I could finally start hearing a little top end. I'll plan on equalization. Also, 120 should not happen very often.Reference is 85db at 40 feet so I should normally need about 105 at1 foot for most material. Only occasional transients should get up into the 120 range.

Thanks for all of the help. I'll report back after the trip to GPA.

Greg

[juniper]

Gil393 damaged audio due to shipping is just no fun.. I had some large horns shipped recently, almost as big as my M19's went to the depot for pick up, and the boxes that were on the pallets, had road scars. Dont know how this stuff happens... I was lucky, the company I choose packs and ships antiques. But still these large and small shipping companies treat shipments not very well.. All I can envision is an overworked, underpayed workforce, that is perpetually pissed off... Sorry for your loss, I am sure you can work it out with the seller... Good luck!!!!

[Alien_Shore]

Sorry, 808-a. They seem to be in good condition but I don't know their history. I'm going to go with the Pascalites. The only two questions are, with or without the backing cap, and should I send them in to GPA for recharge? I'm leaning towards keeping the backing cap, using an 800ish crossover (3rd order) and sending them in. Will I get top end close to a tweeter, keeping in mind I can only hear to 14k?

Yes, you should send them for a re-charge. They're old, and who knows what they've been through. If you're crossing at 800 or better, you can take the loading caps off (if they have them), and they'll sound better. And just like bowtie said, some eq in the mid can help with extending the overall FR. If you have measurement gear, you also can design a custom passive XO for your setup. I did for my garage horns, and I swear the things sound fantastic now. I am finding excuses to just hang out there now