Trouble Driving H&H Bass Speakers - 16ohms / 150W

[Ovation]

Hi All,
I recently posted in the Amplifiers section of this forum as I bought a H&H Amplifier and a pair of Bass Bins (also H&H)..
To summarize, the H&H Amp (m900) drives 450W/channel into a 4ohm load, and when I bought it I was under the belief that the Bins were 300W each at 16ohms.
I've now bridged the H&H amp so that I have a mono block that can put 800w into 8ohms. I've also discovered that the Bins are 150w each not 300w.

Now, I've got the H&H bins wired in parallel so that they put an 8ohm load onto the Amp, but they don't seem to sound too good!!

I posted some details about it here in the amplifier section last week:
http://www.diyaudio.com/forums/showt...027#post578027
... but as yet nobody has replied.

So:
I'm using a Behringer active crossover and I know the Amp works as it's fine for High Frequency stuff. When I try and drive these bins, they just 'rattle' if the bass is quiet, or the amp isn't turned up extremely high.

I've had a look at the drivers in these bins and they look like they just need a hell of a lot of energy to move them.

My Questions:

o If the Amp is 800W @ 8ohms, and the Speakers are rated 150w each at 16ohms wired in parallell - I assume that poking greater than 300W total into the load is not a good idea? The amp seems to need to be at at least 60% volume to geat any output.

o It is normal for a Bass bin to sound totally awful until it is driven at high volume?

o Can anyone comment/explain the design of these boxes (I've attached a crappy diagram - This is a side profile - The left is the back, right is the front. The red thing is the speaker cone which faces the back. The blue dots are very dense stuffing, and the triangle where the cone is mounted appears to be sealed.)

o Does anyone have any specs for these drivers - H&H 1200E 150W @ 16ohms - 12" (I think)

o Is it right that my multimeter reads about 12ohms across these cones - I always expected it to read very close to short!

o What might I replace them with (cheap ish) if it turns out that they're dead?

Any help you can all offer will be much appreciated.

Many Thanks
Jonathan

[Centauri]

Your diagram is typical old-style "W-bin" bass horn - usually quite efficient but won't go much below 60Hz. They shouldn't need much power to get them working well - the bass should be just as clean at low volumes. I would suspect there is something wrong with the drivers. Your measurement of 12ohms would be about right for a 16ohm impedance though.

Would suggest you remove the speakers, and with them sitting on their magnets, gently push on the cone and see if it moves up and down freely without any scraping noises. If this is ok, look carefully for any signs of anything comming unglued, for instance around the outer suspension and the spider suspension near the magnet. Speakers may need repair or recone.

Cheers
Graeme

BTW - I would get rid of that packing inside - a bass horn doesn't need it and it upsets reactance anulling of the chamber.

[Ovation]

That's interesting to know -- I'm not sure about the condition of the horns... I've physically examined one of them, and it looks okay apart from a very small hole in the cone, which I hope isn't detrimental to it's performance.

More intestingly, I have just found out from a company that services lots of H&H stuff that these 1200E speakers were designed for general 'Full Range' PA use and are definately not Bass Drivers.

They also commented that 12" isn't really a very effective size for a bass speaker. - Comments?

I'll try what you suggested and pull these cones right out. They seem quite unresponsive, so I ought to test them as you suggested.

Can you suggest a more compact and more effiective design of bass bin - We will eventually have to cart these around as part of a mobile disco setup, and these bins are really a bit too big (about the size of a washing machine, although not as deep!). (Naturally I may have to buy bigger an better drivers).

I'm also not sure about the ideal xover frequency. My behringer will crossover at anywhere up to 200Hz for the Sub output (or much higher for the 'Low' output).. Any advice for this one?

Thanks again!
Jonathan

[Centauri]

A horn loaded bass cabinet is the most efficient type, but has to be large to work. A smaller cabinet, like ported or bandpass, will require considerably more power to get the same volume. With the right design and the right driver, a 12" will do very well for sub duty in a horn. I don't have parameters for your particular 12, but may work ok in the horn depending on volume level required, but would be most unsuitable for sub use in a ported box.

Yeah, check them out a bit closer - even if they aren't the right match for the horn, at low volume they should still be louder than a normal front loaded box.

Cheers
Graeme

[Ovation]

Hi Everyone,
It's a very long time since I started this thread, but I've finally taken some action and I need some help again.

I've decided the the old H&H 16ohm/150w cones in my bass bins are just no good. They seem pretty knackered anyway, and just rattle when I try to drive them, but I want to run these bins off of a 400W/ch (4ohm) H&H amplifer.
So...

I've gone an bought a pair of 4Ohm Eminence 12" LF Cones to put in the boxes.

When I first posted this, Centuari from Australia mentioned in a post that I should not have any padding inside a horn loaded speaker such as this. I've not tested either way, but I just want to get a second (or third and forth,etc) opinion that this is the right thing to do.

If you read down this post you'll see a crappy cross section that I drew of the speakers.
Please can you fire back your opinions of whether I should leave these bins padded as they are/were or whether I should remove all the nasty fibreglass inside them?

Thanks
Jonathan