audio-talk

Passive pre-amp is now spoken for.

Chris

Hi ya's Chris,

An 'operational' question about the Peavey DECA528, I vaguely remember these coming out and thought about making up a very powerful lightweight 'HiFi' bass combo using one.

Did you find it very quiet in operation? Trouble free?

Cheers

DTB.

Hi Dave,

I used to use it to drive compression drivers in my PA system. The DDT limiters are basically inaudible, which is a nice feature, and it's compact, lightweight, and sounds fine - nothing obviously wrong with the sound, but I haven't given it a serious try in a HiFi application.

If I was to use it in a "serious" application today, I'd probably do a bit of light refurbishment. Maybe replace the bigger electrolytic caps, refresh any thermal paste, etc etc.

The fan might be a bit noisy after sitting in the garage for a while, but IIRC it was pretty quiet in terms of hum/hiss etc. I can try connecting it directly to a compression driver to assess background noise if you like.

All the best,
Chris

Hi ya Chris,

Ta for the feedback (arf!) on what it was like in-use.

When I say 'HiFi bass', I mean in solo bass guitar sense. I've been trying for years to get a crystal clear bass guitar sound live. The closest I've got yet is the 2x10 + HF horn combo with the SWR SuperRedhead. I added another 2 x 10 ext speaker using the same cabinet dimensions as the combo and drove the power amp flat out @ 450w rms (allegedly) into the full 2 Ohm load. It was very inefficient ie. surprisingly not loud but sounded great! The combo weights a ton (ish) though, hence looking into replacing the in-built big heavy valve front-end with Mosfet power amp with a lightweight alternative but keeping the same footprint as the combo (but approximately a ton lighter).

Interesting idea.

I think I'd approach it from the opposite direction: ditch the bass combo, and add a bass-related preamp to a conventional PA system. Some of the best bass tone I've heard has been via a high-impedance DI box.

It's a shame you're not closer to Sheffield - there's a load of PA stuff here that would probably be interesting to try.

Most amps will struggle at 2ohm. I imagine it was a bit louder than running just the combo, but not the +6dB you'd hope for. The Peavey might do better, but it's only going to be a couple of dB either way IMO. Bigger improvements obviously require more considerably power, but then there's the risk to the drivers. Round and round we go!
If there's a PA company nearby, it might be worth borrowing a good 15" 2-way PA speaker to see how that approach works. Make sure it has a decent compression driver (3" diaphragm) or you might be landed with some cheap rubbish.


___________________________________________________

In garage-related news, I've come across a Behringer NU6000 (non-DSP). They bench test at 1200/2000w/ch into 8/4ohm. They seem to be going pretty regularly for £230-250 on eBay. £150 and it's yours.


Chris

Anyone still following along?


A few things have gone, but more stuff has been excavated. How about:

- A pair of Fostex FE166En
- A pair of Dayton 6.5" passive radiators

My plan there was to build a compact, high-efficiency pair of bookshelf speakers with 1x Fostex and 1x PR per side. If you don't add any mass to the PR, a 10L box will tune to around 50Hz, which results in a gradual rolloff down to 50Hz, and then steeper below that. £50 for the Fostex units, and I'll throw in the PRs if you want them.


- A large quantity of Bose 2.5" 4ohm paper-cone full-range drivers. I tried them in a PA-style short line array, but found I didn't like the line-array thing very much. They've sat unused since. They're decent drivers, too. IIRC, they:
- Have a copper cap/sleeve on the pole piece, to keep distortion low
- Are pretty much flat up to 12kHz
- Can withstand a surprisingly large amount of power (~80w peaks) without complaint

Here's an eBay listing which is the same driver: https://www.ebay.co.uk/itm/302871186288 ... 3012096595

Any takers at £5/pair? Again, open to offers.



Stuff coming up over the next few weeks:
- Pair of Fostex PM04 monitors, converted to passive. These have been to a few Owstons and generally did well for themselves. First time was back in 2019, with a 10" subwoofer: https://simonsnewadventuresinhifi.blogs ... -2019.html

More recently, I ran them without a sub, just powered from the big Crown amp:
http://simonsnewadventuresinhifi.blogsp ... -2023.html

They're not getting used much these days, so it'd be good if someone did have some use for them. There's probably £20 in crossover components used, so that's what I'm looking for for them.


For the following, ideally I'd get rid of them in pairs or sets of four. I can remove the drive units if you just want those, but I'd rather not put decent cabinets in the bin. I'd be happy with £25 for each of:

- Four 12" PA speakers, featuring Beyma SM112 and CP230 drive units. Passive crossover with air-cored inductors and poly caps.
The 12" drivers are the previous-version to the SM112/N. The latter has increased power handling, but IIRC the T/S parameters and frequency response are similar. Pretty smooth into the kHz range, sensible roll-off before the treble.
Not much info online about the CP230 tweeters, but they sound reasonably flat/clean.

- Four 8" stage monitors. 8" coaxial, 120w@8ohm each. Considerably nicer than the Viscount ones, since these feature cast-frame drive units and a better crossover. Not much low-end, since they've prioritised efficiency in a small box, so you're probably looking at a 3-way if you want full-range sound. A bigger cabinet might help.
Cabinets are 18mm plywood.

- Pair of 12" coaxial stage monitors, 250w@8ohm each. Similar to the above, but with a 12" driver. Considerably more LF extension.


Chris

chris661 wrote: Sun Oct 27, 2024 6:48 am How about:

- A pair of Fostex FE166En
- A pair of Dayton 6.5" passive radiators

My plan there was to build a compact, high-efficiency pair of bookshelf speakers with 1x Fostex and 1x PR per side. If you don't add any mass to the PR, a 10L box will tune to around 50Hz, which results in a gradual rolloff down to 50Hz, and then steeper below that. £50 for the Fostex units, and I'll throw in the PRs if you want them.

Chris, I'm interested in taking these on, the problem being that I'm down in Somerset - are they boxed and shippable?

Hi Ray,

The drivers & PRs are in their original boxes, but I'd need to find something to ship those in. I'll have a look around here and see what I've got that might work.


Chris

chris661 wrote: Wed Oct 30, 2024 6:49 am Hi Ray,

The drivers & PRs are in their original boxes, but I'd need to find something to ship those in. I'll have a look around here and see what I've got that might work.


Chris

Thanks, Chris, take your time and we'll sort something out when you're ready - I'm not in a hurry.

Ray

Just a quick note that the Fostex monitors mentioned above are now available if anyone fancies them.


Ray, if I can drag myself away from my new speakers (see the Nothing In Particular thread), I'll have a rummage in the garage this afternoon and see what's what.
Will also check the condition of the drivers and upload some pics. Would you like the PRs as well?


Chris

chris661 wrote: Fri Nov 01, 2024 1:42 pm Would you like the PRs as well?

Sorry Chris, I missed this previously. I don't really have a use for the PRs. I'm thinking of using the Fostex units in some 'budget' Frugal Horns.

Ray,

I've just uploaded some pictures of the Fostex units in the DropBox folder.

One of the drivers isn't quite perfect: there's a small dimple on the surround, and what looks like a very fine spray of something on the whizzer.
I've run some signal through them and they're both working as they should, so I don't think there's anything untoward there. Just wanted to make sure you know what you're getting.

Let me know if you're happy with the above, and I'll get some quotes for postage.

All the best,
Chris

Have you got a pair of 12 inch drivers that youll post?

Don't worry if the answer is no , but you don't get with asking

Hi Daniel,

There's the pair of old Wharfedales (W12/EG), some 250w coaxial stage monitors, or the 300w (total) Ecler cabinets. All 12". What sort of thing are you looking for?

Obviously I'd rather keep the drivers in the cabinets for my own ease, but the above have been available for a little while now, so I can look at dismantling something if you really want.


Chris

Obviously me driving to yours isnt an option

So I'm looking for a pair of 12 drivers that can be posted

Wharfedale 12 sounds just the job .