X-over help needed

[polkymon]

Thought I would give this a shot since there are many of you with x-over design experience. I have little or none and only build them.

I have a set of speakers that I have never been pleased with the bass output. I usually have to run a sub with them but they should still have more bass.

If it's possible I would prefer to tweak the x-over and keep the current drivers. The drivers are Ushers, 9950-20 tweeter and 8836A 7" woofer. If I would have to do over again I would have used a smaller woofer and I still may if I can't get the output I want.

The cabinets are curved so it's hard to get an accurate volume but I am guessing in the .30 to .33 cf range ( 8.5 - 9.3L). Front baffle is flat 8 1/2" wide x 15" tall. Rear ported 1 1/2" x 5.5". Drivers are centered.

Specs for tweeter...

http://www.partsexpress.com/pdf/276-608.pdf

for woofer...

http://www.partsexpress.com/pdf/296-606.pdf

Current values for the x-over shown are:

C1= 7.5uF
C2= 10uF
L1= .37mh
L2= .60mh

Zobel= 5.6 ohms , 10 uF

If it isn't possible to improve with the woofer I have I would take suggestions.

Thanks for reading this.

[lndm]

A lack of bass satisfaction can sometimes be due to crossover problems. One possible scenario is that the crossover does not properly compensate for the baffle step, which your room placement partially contributes to. Also there are standing waves and reflections that can cause problems.

So firstly, have you investigated placement, including trying them in the corners and if that isn't the fix, you might play with making the woofer inductor larger as a preliminary tweak to see whether this is it.

[polkymon]

Originally posted by lndm
A lack of bass satisfaction can sometimes be due to crossover problems. One possible scenario is that the crossover does not properly compensate for the baffle step, which your room placement partially contributes to. Also there are standing waves and reflections that can cause problems.

So firstly, have you investigated placement, including trying them in the corners and if that isn't the fix, you might play with making the woofer inductor larger as a preliminary tweak to see whether this is it.

Thank you for the response.

I have found that they are very sensitive to placement. I can only have one in a corner and it does produce more bass than the other. Sitting alone on a table produces hardly any real bass compared to other bookshelfs I have. Maybe its just the nature of the design but its hard to believe it could be that much less.

BTW they also rest on 35" stands which are not changeable.

I will try the inductor suggestion in ther meantime and see if that works. How much more should I increase for a noticable gain? Currently .60mH.

Thanks again.

[lndm]

Originally posted by polkymon it does produce more bass than the other.

Strange, damping material perhaps? Out of spec crossover component maybe? Do you sit centrally in the room?

Sitting alone on a table produces hardly any real bass

BTW they also rest on 35" stands which are not changeable.

The height is one controlling factor. Floor bounce typically causes a null. This is often in the region that gives bass its 'kick'.

How much more should I increase for a noticable gain? Currently .60mH.

Doubling or tripling is all fair game IMO as far as learning your system is concerned. I'm not saying that's what you'll end up with, but you'd at least then learn whether this is the place to fix your problem.

[PeteMcK]

With a Vas of 50 L, perhaps they'd need to be in a larger cabinet to get solid bass?
How about crossing your subs over higher and letting them do some of the mid-bass work?

Pete McK

[polkymon]

Originally posted by lndm
Strange, damping material perhaps? Out of spec crossover component maybe? Do you sit centrally in the room?

The height is one controlling factor. Floor bounce typically causes a null. This is often in the region that gives bass its 'kick'.
Doubling or tripling is all fair game IMO as far as learning your system is concerned. I'm not saying that's what you'll end up with, but you'd at least then learn whether this is the place to fix your problem.

Yes mostly central but I have one in a corner which has better bass response because of it.



Thanks I'll give the coils a try as replacing the driver would be a lot more work.

Originally posted by PeteMcK
With a Vas of 50 L, perhaps they'd need to be in a larger cabinet to get solid bass?
How about crossing your subs over higher and letting them do some of the mid-bass work?

Pete McK

I agree about the larger cabinet. The woofers optimum vb is quoted as .40 cf. and at the time I figured my cabinet at .40-.45. so I thought I was in the ballpark. I am now thinking it is much smaller than that which is why I would consider a smaller vas driver.

I would like to move the set to another room and keep the sub where its at for HT. Where they're going would be a problem adding a sub due to space/WAF.

OT: PE has the Usher tweeter on sale for $45 (was $60). Basically a clone of the Seas 9500 I believe.