where's the bass?

[Guest crazycat]

First off, Thanks! With the all the helpful postings and advice I've recieved from this forum, I just finished rehabing of a pair of long neglected AR 9's. The upgrades were :refinishing the cabinets, refoaming and replacing voice spiders on woofers and lower mid, replacing blown upper mids, replacing all capicators with Solen (except 2500 and 470 uF),upgrading internal wiring, eliminating attunitation swithes, upgrading binding post and adding internal bracing with additional sheet dampning. I reused original coils and fiberglass dampning.

When I first hooked them up, I was blown away ,for about 2 minutes, by the clarity and depth of the sound field. Then my wife noticed the sound was overly bright. Upon investigating both sets of woofers are moving and producing sound, but just at a much lower volume. The effect is like a satellite speaker system without the woofer. Also, one lower mid (8") is not working.

I am powering with vintage Harman Kardon Citation 16 (approx 175 to 200 wpc), so I should have enough power. Where's the bass?? I know that the speakers are placed incorrectly in room, and when I press in on woofer it rebounds a bit quickly, but will that make that much difference? I used rope caulk when replacing speakers.

Any suggestions on bass or how to troubleshoot? What would make mid not work? It reads ok with ohm meter. Any help would be Greatly appreciated.

Thanks

Robert

[ninohernes]

>>when I press in on woofer it rebounds a bit quickly, but will that make that much difference?

Yes it will. When you press in on the cone, it should return slowly. I think that you have more of a problem than that. Double check your wiring in the crossover, and make sure that the woofers are in phase with each other. Working AR9's have enough bass to supply you, and your neighbors with solid response!

>>and adding internal bracing with additional sheet dampning.

I have never been a fan of toying with the original design of AR speakers. Millions of dollars were spent on designing and testing the AR9. It is a tried and true design. The amount dampening was precisely calculated for the given enclosure size, driver size and such. Playing with these numbers can seriously throw the sound off, generally in a bad way. The cabinet should not need more bracing, as it is rigid already, and the fiberglass dampening must be perfect, no more or less than the original. Too much dampening will cause decreased bass response, not enough will cause the speaker to sound boomy and un natural. But the correct amount will produce perfect, tight, natural bass response. Remove the sheet dampening, and really seal the woofers tightly, then your bass (and your neighbors bass :-)) should be back!

[rrcrain]

One of my AR90's had flat bass exactly as you described in your AR9.

It turns out that one of the bass drivers was bad; not dead, just bad.

Mine were also over bright at first after I rebuilt the crossovers. If yours does the same as mine did, they will settle down over the next few months as the caps "break in".

[ar_pro]

The 9 is one system that could never be described as bass-shy. With all due respect, Robert, how good could your rebuilt 9's have sounded ("I was blown away ,for about 2 minutes, by the clarity and depth of the sound field") if one lower midrange was out, and the woofers weren't working properly? Those are serious impairments, buddy!

Our friend Joe is correct in saying that the 9's design is well-tested, and is a finished product. Using more or less than the calculated amount (or a different type) of stuffing will alter the system's performance; as will the addition of sheet dampening. Likewise, additional bracing effectively reduces the cabinet's internal volume, again changing the system's performance. These are not debatable notions, like magic capacitors or wire...if one changes the volume of an acoustic suspension cabinet, one will change the response of the system - period.

I'm not sure what a voice spider is, but a good practice when restoring a system is to individually *test* each driver before installing it in the cabinet...especially if it's been rebuilt, refurbished, reconed, refoamed, etc. This tends to make life easier in the long run, and removes one variable when it comes to troubleshooting.

Assuming your woofers & lower mids haven't been compromised by their restoration, and assuming you've got correct-spec, properly-functioning replacement upper mids, it seems probable that due to the amount of re-wiring, capacitor replacement, and switch removal that you've attempted, the problem is crossover and/or wiring harness-related.

Two questions:

1.) Why did you remove the level controls?

2.) Did you make R and C readings, as well as continuity checks as you went along?

[rrcrain]

He probably removed the level controls after reading several people recommend that he remove them. I did this on my AR90s and do not regret it for one moment.

On the other hand, having installed new crossovers did reveal several of the original drivers were bad, something that wasn't obvious with the old crossovers.

[Guest dogmeninreno]

>He probably removed the level controls after reading several

>people recommend that he remove them. I did this on my AR90s

>and do not regret it for one moment.

>

>On the other hand, having installed new crossovers did reveal

>several of the original drivers were bad, something that

>wasn't obvious with the old crossovers.

What is your logic for removing the level switch circuit? Do you have a perfect placement area in your listening room? Your choice of course but just asking why? Dale

[Guest dogmeninreno]

>First off, Thanks! With the all the helpful postings and

>advice I've recieved from this forum, I just finished rehabing

>of a pair of long neglected AR 9's. The upgrades were

>:refinishing the cabinets, refoaming and replacing voice

>spiders on woofers and lower mid, replacing blown upper mids,

>replacing all capicators with Solen (except 2500 and 470

>uF),upgrading internal wiring, eliminating attunitation

>swithes, upgrading binding post and adding internal bracing

>with additional sheet dampning. I reused original coils and

>fiberglass dampning.

>

>When I first hooked them up, I was blown away ,for about 2

>minutes, by the clarity and depth of the sound field. Then my

>wife noticed the sound was overly bright. Upon investigating

>both sets of woofers are moving and producing sound, but just

>at a much lower volume. The effect is like a satellite

>speaker system without the woofer. Also, one lower mid (8")

>is not working.

>

>I am powering with vintage Harman Kardon Citation 16 (approx

>175 to 200 wpc), so I should have enough power. Where's the

>bass?? I know that the speakers are placed incorrectly in

>room, and when I press in on woofer it rebounds a bit quickly,

>but will that make that much difference? I used rope caulk

>when replacing speakers.

>

>Any suggestions on bass or how to troubleshoot? What would

>make mid not work? It reads ok with ohm meter. Any help would

>be Greatly appreciated.

>Thanks

>Robert

>

>Hello, Have you done a polarity test on your woofers? That could be the problem right there. Also have you verified the output of your amp is connected correctly to both speakers? Someone mentioned that AR used a signal generator set at 15Hz then used a stethescope to listen for air leaks. I think it was Tom Tyson who responded to that. Dale

>

>

>

[ar_pro]

Just asking, but how is it possible to listen to an AR-90, and not be immediately aware that "several of the original drivers were bad"?

As far as disconnecting the switches goes, I number myself among the many who prefer the flexibility that the level controls provide. Dale's point about "perfect placement" is well-made.

[rrcrain]

The original caps had drifted far enough out of spec that the crossover assembly was no longer functioning properly. The upper midrange drivers were literally dead with the lower midrange drivers attempting to reproduce what the upper mids should have been reproducing. Part of the lower midrange spectrum had fallen down into the bass driver section, and the extreme low bass was being totally dropped. This naturally occurred over the cource of 20+ years and my ears adapted to the changes a little at a time as they occurred.

After I had installed the new crossovers, the dead upper midrange driver was glaringly obvious as was the sick but not dead bass driver.

THe AR 9 and 90 speakers are if anything on the warm side. In the 20+ years that I have owned this pair, I have never, used the switches. I've tried them and immediately returned them to zero DB. They are, as far as I and many others are concerned, an unneeded item adding to the complexity of the crossover circuit. If there had been a switch to reduce the bass, that would have been usefull.

[ar_pro]

"The upper midrange drivers were literally dead"

Are you saying that the midrange domes *had no output*, and you couldn't hear this???

[rrcrain]

Yes, thats exactly what I was, and am saying. Even the good driver didn't put out sound with the old crossover. Both speakers sounded the same, until they had new crossovers.

[ar_pro]

>Yes, thats exactly what I was, and am saying. Even the good

>driver didn't put out sound with the old crossover. Both

>speakers sounded the same, until they had new crossovers.

>

Yipes! Trying hard to imagine what an AR-90 would sound like with inoperative upper midrange drivers...you'd think it would be absolutely intolerable - unlistenable, even.

[rrcrain]

Well....

I almost sold them off and bought a pair of Cantons because they sounded so dead, and then I built new crossovers.

The owners of the local audophile shop auditioned my AR90s after they were fully restored, and one guys jaw almost fell off.

I didn't buy the Cantons and they stopped trying to sell them to me.

[Guest Brian_D]

Warm?

Sorry, the 9 is as neutral a speaker as has ever been made.

Numbers don't lie. If your speakers are "warm" there is something wrong.

What is your reference for comparison? Compared to MANY speakers, the 9's are warmer. On the other hand, compared to some others, the 9's are bright.

Your 9's (in top condition of course) should be your reference for this kind of evaluation. All other speakers will be warm or bright compared to this speaker, not the other way around.

-Brian

[rrcrain]

Warm, as in a bit more bass than I care for on occasion given my rooms accoustics.

This is highly dependent upon the source material though. Poory recorded material with exaggerated or heavy bass are notorious offenders. This isn't really the speakers fault though, just my desire to keep the ceiling tile on the ceiling. Ray Montford's "Shed Your Skin" album can be a wall shaker given he uses the double bass.

[Guest Sean]

Acoustic suspension woofers with a properly sealed cabinet should literally "jump" back at you when manually pushed inwards. That's because the air in the box is compressed with nowhere to go, so the internal "spring action" will push the speaker back out. The slower that an acoustic suspension type woofer returns to its' place of rest after being pushed in, the leakier the cabinet. The leakier the cabinet, the less damping the woofers have and the more it acts like a poorly tuned vent. Sean

>

[Guest Sean]

RR, your response is right on the money. If one studies the response curves published by AR or takes actual in-room measurements of 9's or 90's in their actual listening room, they'll find that using any of the padded attenuators simply takes the speaker further away from a neutral response. As such, removing them from the circuit drastically shortens the signal path, lessens the amount of internal wiring, removes the low grade switches and their poor connections from the signal path, etc... The difference in clarity and open-ness of presentation is clearly audible. That is, if one knows what to listen for and is running gear that is of suitable power and clarity for what the 9's and 90's deserve. Further upgrades to the cabinet and crossovers are also quite benefitical to what was an excellent, albeit older technology design. Sean

>

[ninohernes]

When the woofer is pushed out tward to you due to the voice coil pushing out, yes the woofer should go back to rest very quickly. But when you push on the woofer with your hand, you have to press hard to make it go in. In theroy, if the cabinent is completly sealed hermeticly (which is impossible) when pressed in, it would pop right back out. However, paper leaks air, so when you press in, the woofer goes in, slowly, as the air seeps out, and when you let go, it returns slowly as the air seeps back into the cabinent. So a healthy acoustic suspension speaker, will return slowly after being pressed in manually.

[Guest Sean]

Once again, this is completely wrong and full of mis-information. If you're speakers are properly sealed, they will respond as i've mentioned above. If they don't, your speakers aren't sealed so much as they are "slow leakers". I've built sealed speakers from scratch and have modified many existing sealed speakers. All ending up with phenomenally good seals with rapid return rates if the woofers were manually depressed. If they don't "jump" back out, there is no "air-spring" within the box and the whole idea behind Villchur & Kloss' acoustic suspension design is thrown out the window.

As a side note, sealed designs using multiple woofers that share common chambers will not respond as quickly as a single woofer in a well sealed cabinet. That's because the other driver is displacing the air that would normally be compressed, so there is a reduction in the amount of "air spring" under these conditions.

When operating under normal conditions, both woofers would be actively driven, causing them to make equal length excursions. These equal length excursions cause a pressure change within the cabinet, causing the "air spring" to suck the woofers back in with equal force. This does not occur when manually moving one woofer as both woofers are not being actively displaced at the same rate.

In effect, the woofer that is being pushed in is driving the other woofer via pneumatic coupling, much like a passive radiator. Just like a passive radiator system, you run into the action / reaction type of situation, which means that there is a time delay with poor transient response, hence the slow return of the cone. As mentioned, this does not take place in the same fashion when both cones are actively driven due to both motors being actively engaged. Sean

>

[ninohernes]

>Once again, this is completely wrong and full of

>mis-information. If you're speakers are properly sealed, they

>will respond as i've mentioned above. If they don't, your

>speakers aren't sealed so much as they are "slow leakers".

>I've built sealed speakers from scratch and have modified many

>existing sealed speakers. All ending up with phenomenally

>good seals with rapid return rates if the woofers were

>manually depressed. If they don't "jump" back out, there is

>no "air-spring" within the box and the whole idea behind

>Villchur & Kloss' acoustic suspension design is thrown out the

>window.

>

Not really. When the woofer is being depressed manually, there is plenty of time for the air to seep out. When the voice coil is stimulated with any frequency higher than like 5cps, the air has no time to seep out, so the cone is imediatly pulled back to the resting place. Villchur used 15cps and a stethascope to listen for air leaks.

If the cabinent were completly air tight, the cones would move with changes in barometric pressure, which would be very undesirable. Therefore, a well sealed acoustic suspension cabinent must be a slow leaker, to provide for changes in barometric pressure.

[ar_pro]

The "sealed" acoustic suspension enclosure isn't a perfect seal, but it ain't a "slow-leaker" that breathes in-and-out...that would make it sound like a toilet plunger! In fact, a SUDDEN change in barometric pressure *would* cause a properly-sealed AS woofer to move. The described "quick-return" is a desired trait of a properly-functioning AS woofer. I'd suggest consulting any college Physics text for further info on this notion.

[ninohernes]

Correct, but it does breathe, just very slowly as I stated above. And yes, the woofer will move with barometric pressure changes, but the pressure will eventually equalize.

[johnieo]

Perhaps there is some confusion in the above subthread as I sense tapping and displacing are being mingled.

If one thumps or taps a woofer in free air, it will move and return to its rest position very quickly, perhaps oscillating once or twice. This is the natural resonance of the mass of the cone. If one now places this woofer in a sealed box, and taps--not displaces it--it will also come to rest quickly, aided by the air pressure. The addition of fiberglas to the inside of the chamber will not affect this time constant as air moves with ease through it on that time scale. A RAPID return after a tap is a sign of a highly compliant woofer suspension and excellent high-frequency acoustic suspension.

Displacing the cone--holding it depressed for a second or two then releasing it--is totally different from tapping, as the starting condition is different. After the cone is displaced, air leaks inward through the small spaces around the potentiometers and the inside / outside pressures soon equalize. When released, the pressure drops, then returns to atmospheric with a time constant determined by the volume of the cabinet divided by this leak rate (same rate at which the air exited). The smaller the leak rate, the longer it takes to recover--about 1-2 s seems typical for a 1.7 cf cabinet. A SLOW return after displacement is a sign of excellent low-frequency acoustic suspension. As others have pointed out in earlier posts, the cabinet needs to be airtight to very low frequencies, but not to dc!

A woofer's low frequency response can be compromised by either a putty leak or a permeable foam surround. If one sprays water or Armorall on a foam surround (both evaporate in minutes) and the recovery time suddenly increases from a fraction of a second to 1-2 s, it's an indication of permeable foam and not a leaky putty seal. Either leak can affect the low frequency performance of an AR. Villchur's technique of using an 18 Hz square wave and stethoscope is a great way to locate putty and hot glue leaks, but it would not sense foam permeation.