Help for Upgrading JBL HSL810's Needed

[techbiker]

Originally Posted by River757

techbiker: based on your additional descriptions, I am 99.9% sure the tweeters are damaged or completely blown.

Also, it doesn't matter what the shape of the horn is or how much they cost or much the driver itself cost, because simply placing them together will cause some type of interaction. And that small "cap" suspended above the tweeter dome also interacts with the output of the dome IIRC usually to correct some type of phase problem; plus, every time I've seen this dome tweeter, all the way back to its introduction around 1983, it has included that cap (and since it is not attractive in any way it is not just a cosmetic addition).

Me? I would buy the JBL tweeter replacements and call it a day. They may look the same as a $5 version sold on a retail site, but JBL may have had their version customized for use in that particular speaker series and possibly even that specific model. This is a common scenario in the commercial speaker world, going back decades (though JBL's best models usually use drivers built by JBL themselves).

Oh I see. I wasn't sure if the cap was strictly for the protection of the tweeter or if it did serve some acoustic purpose.

The most important thing though is how I should go about protecting these tweeters from future damage if I purchase JBL replacements. I wouldn't want to sink a $60 investment if something happens to my amplifier that stresses out these speakers. Is there something that I could install to prevent power spikes from damaging these fragile tweeters?

And by the way, the set of 410's that I was using previously had the same problem. I guess that I couldn't tell that the tweeters were having issues since the 4" drivers in that model were able to compensate.

Thanks again.

[techbiker]

*bump*

Does anyone know of a way to protect these tweeters from damage if I purchase the delicate stock ones?

Otherwise, I'm probably just going to hack up the plastic horn pieces to enable them to fit competent, high-quality tweeters.

Thanks

[dabbler]

You could wire a polyswitch in series with the tweeter. Cheap and easy fix.

[techbiker]

Originally Posted by dabbler

You could wire a polyswitch in series with the tweeter. Cheap and easy fix.

Dabbler, thanks for the recommendation. I will make sure to install an appropriate polyswitch when I get around to it.

I got my amplifier back to working condition last night (I had to find a way to run shielded cables from the balanced input on the amplifier to the unbalanced output of a laptop). Anyway, I had a chance to audition the 810's again and it actually seems like the tweeters are working decently. In comparison with my SP-BL41LR's, the tweeters on the 810's don't seem to be able to reach down low enough to match the woofers in these speakers and or the woofers cannot reach high enough to hand-off to the tweeters.

I checked the crossovers and there is a polypropylene capacitor in series with the tweeters, so I am not worried about that being a problem anymore.

The woofers on the 810's on the other hand are rather poor. From about 100hz to 600hz, the 8" woofers work efficiently, however anything between about 1000hz and 2600hz (where the tweeters come in) is just not represented well. I would say that there is a 1600hz gap in which the speakers are not representing my audio faithfully and where overall volume diminishes. Even at 2600hz, the tweeters are beginning to break up a bit (I do not believe that they should be crossed at 2600hz for an optimally-flat frequency response). I have had multiple people confirm this problem.

Therefore, I propose the following: Since the same exact tweeter is crossed over at 3000hz in the JBL 410's, I would raise the crossover to 3000hz and replace the woofers with more competent (better) woofers that are able to maintain a flat frequency response up to around 2600-3000hz. I don't mind sacrificing a bit of low-end since I have a Paradigm SB-90 subwoofer that will cover anything between about 30hz and 90hz well. Thus, I might look for a woofer that will respond well from between about 120hz and 3000hz if possible.

This SHOULD fix my problem. What do you guys think? Do you have any woofers that you would recommend and could I just raise the crossover frequency by changing out the poly capacitors that are in-line with the tweeters? Finally, since these woofers are not part of horns, am I correct when I say that I shouldn't have to worry as much about their interaction with the horn component?

I could leave the crossover point at 2600hz if you believe that the larger plastic horns in the 810's vs the 410's are somehow optimizing these tweeters for a lower crossover frequency, however I don't see how raising the crossover into the tweeters' "sweet spots" should harm anything.

Here is a rough frequency response graph that illustrates what I am talking about:



Edit: After some searching on Partsexpress, it's VERY hard to find a decent 8" woofer with a relatively flat frequency response up to 2600hz, let alone 3000hz! Since the stock woofer is so inexpensive, I can only imagine that this gap I am hearing is quite substantial!

[River757]

tweeter protector lamp - I've seen these used in a few speakers over the years but you need to know how much power the specific tweeter uses to pick the right protector lamp.......

[dabbler]

The woofers on the 810's on the other hand are rather poor. From about 100hz to 600hz, the 8" woofers work efficiently, however anything between about 1000hz and 2600hz (where the tweeters come in) is just not represented well. I would say that there is a 1600hz gap in which the speakers are not representing my audio faithfully and where overall volume diminishes. Even at 2600hz, the tweeters are beginning to break up a bit (I do not believe that they should be crossed at 2600hz for an optimally-flat frequency response). I have had multiple people confirm this problem.

Post the measurements so we can see whats going on

[system7]

I'm struggling to follow this, but it seems JBL have fitted an 8" 4.4 ohm polypropylene woofer to a horn-loaded puny 5.5 ohm mylar tweeter. I get a crossover around 5000Hz on the 5.5ohm tweeter.

That shunt 0.33mH/30uF trap is an odd thing to fit. It seems to boost output around 1600Hz. If it was like a bextrene KEF B200 bass, you'd probably fit a simple shunt 7uF capacitor across the bass filter and do without the trap and the 33uF.

What is odd, is that you really shouldn't be expecting an 8" bass to cover up to 5000Hz. That and the plastic horn must sound horrible!

[dabbler]

Its a poor design, not really worth tinkering with. One option would be to remove the horn altogether and fit a waveguide and compression driver using mini-econowave crossover. But it lookls like the horn is glued on.

[techbiker]

System7, thanks for the helpful post!

And yes, it does appear that JBL hoped that all of the horribleness in these speakers would blend itself into an acceptable mediocrity when combined with a large enough subwoofer lol.

I didn't buy these speakers to serve as part of my primary sound system so I was never aiming for excellent sound however. In fact, I was originally hoping to get some advice as to what I should look at for replacement tweeters to make these speakers sound acceptable. I don't care if I have to ball-park the adjustments because I'm pretty sure that almost anything will improve sound quality lol.

I could replace the horn and tweeter with a waveguide and compression driver first before fiddling with the woofer. What cost-effective driver and horn would you recommend using? Of course, I will measure the hole to find the exact size of horn required. Also, what crossover frequency should I be aiming for when I build a crossover?

By the way, this cheap plastic horn might be glued on, but it WILL come off one way or another.

Finally, the cabinets are actually quite nice (they come with quality speaker cable posts too) and I think that the speakers look quite acceptable from the outside. Just because of this, I think that they are worth fiddling with.

Edit: I found a really inexpensive horn driver that is getting great reviews on Partsexpress:

http://www.parts-express.com/pe/show...number=270-069

A guy called speaker-guy posted this recommendation for a crossover:

Build a second order Linkwitz-Riley 2000 HZ crossover for these drivers and hear them come alive!
Step 1: Use 2 - (20 watt, 20 ohm) resistors part number 017-20. Twist them together in parallel getting a 40-watt at 10-ohm load. Solder them across the Driver terminals.
Step 2: Also place a 1.5 mH Coil - Part Number 255-426 across the Driver terminals with the resistors.
Step 3: Because we are creating a second order crossover which inverts the phase 180 degrees, place a 4 uF capacitor (part number 027-421) in-line from the source (+) lead to the (-) terminal on your horn driver. Connect the ground (-) wire to the hot (+) lead of the horn driver
This allows you to couple this horn driver with a speaker / woofer without using a crossover to stop the woofer from going as far up in frequency as it can. The phase is linear complimenting the full spectrum without peaks.

What do you think about combining this with the stock 8 inch woofer?

[system7]

I'd dump the horn idea altogether. Especially for a speaker with a mere 89dB sensitivity. Just my opinion though.

In essence you need to measure the hole in the baffle and figure what better tweeter you can fit. Maybe a 104 or 110mm jobbie would do it. Don't know. But most tweeters get near 90dB.

You could do worse than fit a waveguide Monacor DT-300 IMO. Pad it a bit to get the efficiency down though.
Vifa C17WH-

The polypropylene bass ought to be OK with a lowish crossover.